diff --git a/CHANGELOG.md b/CHANGELOG.md
index 839d69ccc..6cfbf3cc7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Changed
+
+- Deprecated `firstOrderDate` in favor of `dateOfFirstActivity` in the `GET api/v2/portfolio/performance` endpoint
+
 ## 3.34.0 - 2026-07-25
 
 ### Changed
diff --git a/apps/api/src/app/portfolio/portfolio.service.ts b/apps/api/src/app/portfolio/portfolio.service.ts
index ca4ead8b8..6c527ed2b 100644
--- a/apps/api/src/app/portfolio/portfolio.service.ts
+++ b/apps/api/src/app/portfolio/portfolio.service.ts
@@ -1034,6 +1034,7 @@ export class PortfolioService {
     if (accountBalanceItems.length === 0 && activities.length === 0) {
       return {
         chart: [],
+        dateOfFirstActivity: undefined,
         firstOrderDate: undefined,
         hasErrors: false,
         performance: {
@@ -1091,6 +1092,7 @@ export class PortfolioService {
       chart,
       errors,
       hasErrors,
+      dateOfFirstActivity: parseDate(historicalData[0]?.date),
       firstOrderDate: parseDate(historicalData[0]?.date),
       performance: {
         netPerformance,
diff --git a/apps/client/src/app/pages/portfolio/analysis/analysis-page.component.ts b/apps/client/src/app/pages/portfolio/analysis/analysis-page.component.ts
index 5fa952a4f..990816193 100644
--- a/apps/client/src/app/pages/portfolio/analysis/analysis-page.component.ts
+++ b/apps/client/src/app/pages/portfolio/analysis/analysis-page.component.ts
@@ -110,7 +110,7 @@ export class GfAnalysisPageComponent implements OnInit {
   private readonly deviceType = computed(
     () => this.deviceDetectorService.deviceInfo().deviceType
   );
-  private firstOrderDate: Date;
+  private dateOfFirstActivity: Date;
 
   private readonly changeDetectorRef = inject(ChangeDetectorRef);
   private readonly clipboard = inject(Clipboard);
@@ -302,8 +302,8 @@ export class GfAnalysisPageComponent implements OnInit {
         range: this.user?.settings?.dateRange ?? DEFAULT_DATE_RANGE
       })
       .pipe(takeUntilDestroyed(this.destroyRef))
-      .subscribe(({ chart, firstOrderDate, performance }) => {
-        this.firstOrderDate = firstOrderDate ?? new Date();
+      .subscribe(({ chart, dateOfFirstActivity, performance }) => {
+        this.dateOfFirstActivity = dateOfFirstActivity ?? new Date();
 
         this.investments = [];
         this.performance = performance;
@@ -416,7 +416,7 @@ export class GfAnalysisPageComponent implements OnInit {
             symbol,
             filters: this.userService.getFilters(),
             range: this.user?.settings?.dateRange ?? DEFAULT_DATE_RANGE,
-            startDate: this.firstOrderDate
+            startDate: this.dateOfFirstActivity
           })
           .pipe(takeUntilDestroyed(this.destroyRef))
           .subscribe(({ marketData }) => {
diff --git a/libs/common/src/lib/interfaces/responses/portfolio-performance-response.interface.ts b/libs/common/src/lib/interfaces/responses/portfolio-performance-response.interface.ts
index b0c453514..104302de3 100644
--- a/libs/common/src/lib/interfaces/responses/portfolio-performance-response.interface.ts
+++ b/libs/common/src/lib/interfaces/responses/portfolio-performance-response.interface.ts
@@ -4,6 +4,12 @@ import { ResponseError } from './errors.interface';
 
 export interface PortfolioPerformanceResponse extends ResponseError {
   chart?: HistoricalDataItem[];
+  dateOfFirstActivity: Date;
+
+  /**
+   * @deprecated Use `dateOfFirstActivity` instead
+   */
   firstOrderDate: Date;
+
   performance: PortfolioPerformance;
 }
diff --git a/libs/ui/src/lib/services/data.service.ts b/libs/ui/src/lib/services/data.service.ts
index 5492794d7..23c654ae6 100644
--- a/libs/ui/src/lib/services/data.service.ts
+++ b/libs/ui/src/lib/services/data.service.ts
@@ -716,8 +716,10 @@ export class DataService {
       })
       .pipe(
         map((response) => {
-          if (response.firstOrderDate) {
-            response.firstOrderDate = parseISO(response.firstOrderDate);
+          if (response.dateOfFirstActivity) {
+            response.dateOfFirstActivity = parseISO(
+              response.dateOfFirstActivity
+            );
           }
 
           return response;