diff --git a/CHANGELOG.md b/CHANGELOG.md
index 483112c2d7..8f8ac772e4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -42,6 +42,7 @@ This release adds an embedded SQLite database for storing metadata required by t
 1. [21800](https://github.com/influxdata/influxdb/pull/21800): Return an error instead of panicking when InfluxQL statement rewrites fail.
 1. [21840](https://github.com/influxdata/influxdb/pull/21840): Run migrations on restored bolt & SQLite metadata databases as part of the restore process.
 1. [21844](https://github.com/influxdata/influxdb/pull/21844): Upgrade to latest version of `influxdata/cron` so that tasks can be created with interval of `every: 1w`.
+1. [21849](https://github.com/influxdata/influxdb/pull/21849): Specify which fields are missing when rejecting an incomplete onboarding request.
 
 ## v2.0.7 [2021-06-04]
 
diff --git a/tenant/error.go b/tenant/error.go
index ee9beb04f0..90ec96cb03 100644
--- a/tenant/error.go
+++ b/tenant/error.go
@@ -34,11 +34,6 @@ var (
 		Msg:  "onboarding has already been completed",
 	}
 
-	ErrOnboardInvalid = &errors.Error{
-		Code: errors.EEmptyValue,
-		Msg:  "onboard failed, missing value",
-	}
-
 	ErrNotFound = &errors.Error{
 		Code: errors.ENotFound,
 		Msg:  "not found",
diff --git a/tenant/service_onboarding.go b/tenant/service_onboarding.go
index 09acf1b806..18988c5015 100644
--- a/tenant/service_onboarding.go
+++ b/tenant/service_onboarding.go
@@ -3,8 +3,10 @@ package tenant
 import (
 	"context"
 	"fmt"
+	"strings"
 
 	"github.com/influxdata/influxdb/v2/kit/platform"
+	"github.com/influxdata/influxdb/v2/kit/platform/errors"
 
 	"github.com/influxdata/influxdb/v2"
 	icontext "github.com/influxdata/influxdb/v2/context"
@@ -85,8 +87,28 @@ func (s *OnboardService) OnboardInitialUser(ctx context.Context, req *influxdb.O
 
 // onboardUser allows us to onboard new users.
 func (s *OnboardService) onboardUser(ctx context.Context, req *influxdb.OnboardingRequest, permFn func(orgID, userID platform.ID) []influxdb.Permission) (*influxdb.OnboardingResults, error) {
-	if req == nil || req.User == "" || req.Org == "" || req.Bucket == "" {
-		return nil, ErrOnboardInvalid
+	if req == nil {
+		return nil, &errors.Error{
+			Code: errors.EEmptyValue,
+			Msg:  "onboarding failed: no request body provided",
+		}
+	}
+
+	var missingFields []string
+	if req.User == "" {
+		missingFields = append(missingFields, "username")
+	}
+	if req.Org == "" {
+		missingFields = append(missingFields, "org")
+	}
+	if req.Bucket == "" {
+		missingFields = append(missingFields, "bucket")
+	}
+	if len(missingFields) > 0 {
+		return nil, &errors.Error{
+			Code: errors.EUnprocessableEntity,
+			Msg:  fmt.Sprintf("onboarding failed: missing required fields [%s]", strings.Join(missingFields, ",")),
+		}
 	}
 
 	result := &influxdb.OnboardingResults{}
diff --git a/testing/onboarding.go b/testing/onboarding.go
index c91048d5bd..12bccce4ad 100644
--- a/testing/onboarding.go
+++ b/testing/onboarding.go
@@ -85,7 +85,7 @@ func OnboardInitialUser(
 				},
 			},
 			wants: wants{
-				errCode: errors.EEmptyValue,
+				errCode: errors.EUnprocessableEntity,
 			},
 		},
 		{
@@ -104,7 +104,7 @@ func OnboardInitialUser(
 				},
 			},
 			wants: wants{
-				errCode: errors.EEmptyValue,
+				errCode: errors.EUnprocessableEntity,
 			},
 		},
 		{
@@ -123,26 +123,7 @@ func OnboardInitialUser(
 				},
 			},
 			wants: wants{
-				errCode: errors.EEmptyValue,
-			},
-		},
-		{
-			name: "missing password should fail",
-			fields: OnboardingFields{
-				IDGenerator: &loopIDGenerator{
-					s: []string{oneID, twoID, threeID, fourID},
-				},
-				TokenGenerator: mock.NewTokenGenerator(oneToken, nil),
-				IsOnboarding:   true,
-			},
-			args: args{
-				request: &platform.OnboardingRequest{
-					User: "admin",
-					Org:  "org1",
-				},
-			},
-			wants: wants{
-				errCode: errors.EEmptyValue,
+				errCode: errors.EUnprocessableEntity,
 			},
 		},
 		{