diff --git a/src/app.module.ts b/src/app.module.ts
index 0db00ed..7874216 100644
--- a/src/app.module.ts
+++ b/src/app.module.ts
@@ -2,6 +2,8 @@ import { Module } from '@nestjs/common';
 import { ConfigModule } from '@nestjs/config';
 import { APP_FILTER, APP_GUARD, APP_INTERCEPTOR } from '@nestjs/core';
 import { ThrottlerModule, ThrottlerGuard } from '@nestjs/throttler';
+import { ServeStaticModule } from '@nestjs/serve-static';
+import { join } from 'path';
 import { HealthModule } from './health/health.module';
 import { PrismaModule } from './prisma/prisma.module';
 import { AuthModule } from './auth/auth.module';
@@ -28,6 +30,7 @@ import { SchedulerModule } from './scheduler/scheduler.module';
 import { AccountingModule } from './accounting/accounting.module';
 import { PayrollModule } from './payroll/payroll.module';
 import { RoleModule } from './role/role.module';
+import { CommentModule } from './comment/comment.module';
 import { GlobalExceptionFilter } from './common/filters/http-exception.filter';
 import { ResponseInterceptor } from './common/interceptors/response.interceptor';
 import { PermissionsGuard } from './common/guards/permissions.guard';
@@ -69,6 +72,11 @@ import { AccessGuard } from './common/guards/access.guard';
     AccountingModule,
     PayrollModule,
     RoleModule,
+    CommentModule,
+    ServeStaticModule.forRoot({
+      rootPath: join(__dirname, '..', 'uploads'),
+      serveRoot: '/uploads',
+    }),
   ],
   providers: [
     { provide: APP_FILTER, useClass: GlobalExceptionFilter },
diff --git a/src/comment/comment.controller.ts b/src/comment/comment.controller.ts
new file mode 100644
index 0000000..7ac6e35
--- /dev/null
+++ b/src/comment/comment.controller.ts
@@ -0,0 +1,52 @@
+import {
+  Controller,
+  Get,
+  Post,
+  Param,
+  Body,
+  UseGuards,
+  UseInterceptors,
+  UploadedFiles,
+} from '@nestjs/common';
+import { AuthGuard } from '@nestjs/passport';
+import { FileFieldsInterceptor } from '@nestjs/platform-express';
+import { CommentService } from './comment.service';
+import { CreateCommentDto } from './dto/create-comment.dto';
+import { Roles } from '../common/decorators/roles.decorator';
+import { RolesGuard } from '../common/guards/roles.guard';
+import { TenantGuard } from '../common/guards/tenant.guard';
+import { CurrentUser, CurrentUserPayload } from '../common/decorators/current-user.decorator';
+import { multerOptions } from '../common/multer/multer.config';
+
+@Controller('tickets/:ticketId/comments')
+@UseGuards(AuthGuard('jwt'), TenantGuard, RolesGuard)
+export class CommentController {
+  constructor(private readonly commentService: CommentService) {}
+
+  @Get()
+  @Roles('technician')
+  async findAll(
+    @CurrentUser() user: CurrentUserPayload,
+    @Param('ticketId') ticketId: string,
+  ) {
+    return this.commentService.findAll(user.tenantId, ticketId);
+  }
+
+  @Post()
+  @Roles('technician')
+  @UseInterceptors(FileFieldsInterceptor([{ name: 'files', maxCount: 3 }], multerOptions))
+  async create(
+    @CurrentUser() user: CurrentUserPayload,
+    @Param('ticketId') ticketId: string,
+    @Body() dto: CreateCommentDto,
+    @UploadedFiles() files?: { files?: Express.Multer.File[] },
+  ) {
+    return this.commentService.create(
+      user.tenantId,
+      ticketId,
+      user.sub,
+      dto.content,
+      files?.files,
+    );
+  }
+}
diff --git a/src/comment/comment.module.ts b/src/comment/comment.module.ts
new file mode 100644
index 0000000..d742b1b
--- /dev/null
+++ b/src/comment/comment.module.ts
@@ -0,0 +1,13 @@
+import { Module } from '@nestjs/common';
+import { CommentController } from './comment.controller';
+import { CommentService } from './comment.service';
+import { PrismaModule } from '../prisma/prisma.module';
+import { NotificationModule } from '../notification/notification.module';
+
+@Module({
+  imports: [PrismaModule, NotificationModule],
+  controllers: [CommentController],
+  providers: [CommentService],
+  exports: [CommentService],
+})
+export class CommentModule {}
diff --git a/src/comment/comment.service.ts b/src/comment/comment.service.ts
new file mode 100644
index 0000000..bf4ca0e
--- /dev/null
+++ b/src/comment/comment.service.ts
@@ -0,0 +1,117 @@
+import { Injectable, NotFoundException } from '@nestjs/common';
+import { PrismaService } from '../prisma/prisma.service';
+import { NotificationService } from '../notification/notification.service';
+
+@Injectable()
+export class CommentService {
+  constructor(
+    private readonly prisma: PrismaService,
+    private readonly notificationService: NotificationService,
+  ) {}
+
+  async findAll(tenantId: string, ticketId: string) {
+    const db = this.prisma.forTenant(tenantId);
+    const ticket = await db.ticket.findFirst({ where: { id: ticketId } });
+    if (!ticket) throw new NotFoundException('Ticket not found');
+
+    return this.prisma.ticketComment.findMany({
+      where: { tenantId, ticketId },
+      include: {
+        author: { select: { id: true, firstName: true, lastName: true } },
+        attachments: true,
+      },
+      orderBy: { createdAt: 'asc' },
+    });
+  }
+
+  async create(
+    tenantId: string,
+    ticketId: string,
+    userId: string,
+    content: string,
+    files?: Express.Multer.File[],
+  ) {
+    const db = this.prisma.forTenant(tenantId);
+    const ticket = await db.ticket.findFirst({ where: { id: ticketId } });
+    if (!ticket) throw new NotFoundException('Ticket not found');
+
+    const comment = await this.prisma.ticketComment.create({
+      data: {
+        tenantId,
+        ticketId,
+        userId,
+        content,
+        attachments: files?.length
+          ? {
+              create: files.map((f) => ({
+                fileName: f.originalname,
+                filePath: f.filename,
+                fileType: f.mimetype,
+                fileSize: f.size,
+              })),
+            }
+          : undefined,
+      },
+      include: {
+        author: { select: { id: true, firstName: true, lastName: true } },
+        attachments: true,
+      },
+    });
+
+    // Parse @mentions and notify mentioned users
+    const mentions = this.parseMentions(content);
+    if (mentions.length > 0) {
+      const db2 = this.prisma.forTenant(tenantId);
+      const users = await db2.user.findMany({
+        where: { tenantId, isActive: true },
+        select: { id: true, firstName: true, lastName: true },
+      });
+
+      const commenterName = `${comment.author.firstName} ${comment.author.lastName}`;
+
+      for (const mention of mentions) {
+        const mentionedUser = users.find(
+          (u) =>
+            `${u.firstName} ${u.lastName}`.toLowerCase() === mention.toLowerCase() ||
+            u.firstName.toLowerCase() === mention.toLowerCase(),
+        );
+        if (mentionedUser && mentionedUser.id !== userId) {
+          await this.notificationService.create(tenantId, {
+            userId: mentionedUser.id,
+            type: 'in_app',
+            channel: 'mention',
+            title: 'You were mentioned',
+            message: `${commenterName} mentioned you in "${ticket.title}"`,
+            ticketId,
+          });
+        }
+      }
+    }
+
+    // Notify ticket creator (if not the commenter)
+    if (ticket.createdById && ticket.createdById !== userId) {
+      const commenterName = `${comment.author.firstName} ${comment.author.lastName}`;
+      await this.notificationService.create(tenantId, {
+        userId: ticket.createdById,
+        type: 'in_app',
+        channel: 'comment_added',
+        title: 'New comment on your ticket',
+        message: `${commenterName} commented on "${ticket.title}"`,
+        ticketId,
+      });
+    }
+
+    return comment;
+  }
+
+  /** Extract @FirstName or @FirstNameLastName from content */
+  private parseMentions(content: string): string[] {
+    const regex = /@(\w+(?:\s+\w+)?)/g;
+    const matches: string[] = [];
+    let match: RegExpExecArray | null;
+    while ((match = regex.exec(content)) !== null) {
+      matches.push(match[1]);
+    }
+    return [...new Set(matches)];
+  }
+}
diff --git a/src/comment/dto/create-comment.dto.ts b/src/comment/dto/create-comment.dto.ts
new file mode 100644
index 0000000..fdc01a5
--- /dev/null
+++ b/src/comment/dto/create-comment.dto.ts
@@ -0,0 +1,7 @@
+import { IsString, MinLength } from 'class-validator';
+
+export class CreateCommentDto {
+  @IsString()
+  @MinLength(1)
+  content!: string;
+}
diff --git a/src/common/multer/multer.config.ts b/src/common/multer/multer.config.ts
new file mode 100644
index 0000000..9630c56
--- /dev/null
+++ b/src/common/multer/multer.config.ts
@@ -0,0 +1,30 @@
+import { MulterOptions } from '@nestjs/platform-express/multer/interfaces/multer-options.interface';
+import { diskStorage } from 'multer';
+import { extname } from 'path';
+
+export const multerOptions: MulterOptions = {
+  storage: diskStorage({
+    destination: './uploads',
+    filename: (_req, file, cb) => {
+      const uniqueSuffix = Date.now() + '-' + Math.round(Math.random() * 1e9);
+      cb(null, uniqueSuffix + extname(file.originalname));
+    },
+  }),
+  limits: {
+    fileSize: 5 * 1024 * 1024, // 5MB per file
+  },
+  fileFilter: (_req, file, cb) => {
+    const allowed = [
+      'image/jpeg',
+      'image/png',
+      'image/gif',
+      'image/webp',
+      'application/pdf',
+    ];
+    if (allowed.includes(file.mimetype)) {
+      cb(null, true);
+    } else {
+      cb(new Error(`File type ${file.mimetype} not allowed`), false);
+    }
+  },
+};
diff --git a/src/notification/notification.service.ts b/src/notification/notification.service.ts
index 67e62e0..bf5050f 100644
--- a/src/notification/notification.service.ts
+++ b/src/notification/notification.service.ts
@@ -40,6 +40,7 @@ export class NotificationService {
     channel: string;
     title: string;
     message: string;
+    ticketId?: string;
   }) {
     return this.prisma.notification.create({
       data: {
@@ -50,6 +51,7 @@ export class NotificationService {
         channel: data.channel,
         title: data.title,
         message: data.message,
+        ticketId: data.ticketId,
         sentAt: new Date(),
       },
     });
diff --git a/src/ticket/ticket.service.ts b/src/ticket/ticket.service.ts
index c759cd0..81987b9 100644
--- a/src/ticket/ticket.service.ts
+++ b/src/ticket/ticket.service.ts
@@ -4,6 +4,7 @@ import {
   BadRequestException,
 } from '@nestjs/common';
 import { PrismaService } from '../prisma/prisma.service';
+import { NotificationService } from '../notification/notification.service';
 import { CreateTicketDto } from './dto/create-ticket.dto';
 import { UpdateTicketDto } from './dto/update-ticket.dto';
 
@@ -20,7 +21,10 @@ export class TicketService {
   onTicketResolved: ((event: TicketResolvedEvent) => Promise<void>) | null =
     null;
 
-  constructor(private readonly prisma: PrismaService) {}
+  constructor(
+    private readonly prisma: PrismaService,
+    private readonly notificationService: NotificationService,
+  ) {}
 
   async findAll(tenantId: string, filters?: { clientId?: string; status?: string; type?: string }) {
     const db = this.prisma.forTenant(tenantId);
@@ -111,6 +115,18 @@ export class TicketService {
       });
     }
 
+    // Notify newly assigned user
+    if (dto.assigneeId && dto.assigneeId !== existing.assigneeId) {
+      this.notificationService.create(tenantId, {
+        userId: dto.assigneeId,
+        type: 'in_app',
+        channel: 'ticket_assigned',
+        title: 'Ticket assigned to you',
+        message: `You were assigned to "${existing.title}"`,
+        ticketId: id,
+      }).catch(() => {}); // non-blocking
+    }
+
     return this.prisma.ticket.update({
       where: { id },
       data: {