Lesson 2 — Microsoft Sentinel vs Microsoft Defender XDR
One of the most common questions in Microsoft security is simple:
If I already have Microsoft Defender XDR, why would I also need Microsoft Sentinel?
The answer is that Microsoft Defender XDR and Microsoft Sentinel are not competing products.
They solve different problems, and in many mature security environments they work together.
What you will learn
This lesson clears up the difference between Microsoft Sentinel and Microsoft Defender XDR in practical SOC language.
Learning objectives
After completing this lesson, you should be able to explain the role of each platform clearly.
- Describe Microsoft Defender XDR in simple terms.
- Describe Microsoft Sentinel in simple terms.
- Understand where the platforms overlap.
- Know when Defender XDR is the right tool.
- Know when Sentinel is the right tool.
- Understand why many security teams use both together.
The question everyone asks
The question usually sounds like this:
“Do we need Microsoft Sentinel if we already have Microsoft Defender XDR?”
The short answer is: it depends on how broad your security operations need to be. Defender XDR is focused on Microsoft security workloads. Sentinel is designed for wider SIEM and SOAR operations.
What is Microsoft Defender XDR?
Microsoft Defender XDR is Microsoft's extended detection and response platform. It brings together security signals across Microsoft Defender products and helps analysts investigate threats inside the Microsoft security ecosystem.
- Microsoft Defender for Endpoint
- Microsoft Defender for Office 365
- Microsoft Defender for Identity
- Microsoft Defender for Cloud Apps
- Microsoft Entra ID identity signals
What is Microsoft Sentinel?
Microsoft Sentinel is Microsoft's cloud-native SIEM and SOAR platform. It can ingest data from Microsoft sources, third-party products, cloud platforms, network devices and custom applications.
- Microsoft Defender XDR
- Azure Activity and Entra ID logs
- Firewalls and network devices
- Linux, Syslog and servers
- AWS, third-party clouds and custom logs
Visual comparison
The easiest way to understand the difference is to think about scope.
| Microsoft Defender XDR | Microsoft Sentinel |
|---|---|
| Extended Detection and Response platform. | Cloud-native SIEM and SOAR platform. |
| Focused on Microsoft security workloads. | Designed for Microsoft and third-party telemetry. |
| Excellent for endpoint, email, identity and cloud app investigations. | Excellent for enterprise-wide correlation, dashboards, hunting and automation. |
| Provides Microsoft-native incidents and alert correlation. | Builds SOC workflows across many data sources. |
How they work together
Defender XDR can detect and correlate activity across Microsoft Defender products. Sentinel can then ingest those incidents and combine them with wider organisational telemetry.
Real-world example
A phishing email arrives. Defender for Office 365 detects the message and Defender XDR correlates the email, user and endpoint activity into an incident.
Sentinel can then add wider context: firewall traffic, VPN sessions, risky sign-ins, cloud activity, third-party logs and automated response steps.
Do they compete?
No. This is the key point.
Defender XDR is the Microsoft-native XDR layer. Sentinel is the enterprise SIEM and SOAR layer.
In a mature SOC, Defender XDR often provides high-quality Microsoft security incidents, while Sentinel provides the broader operational view.
When should you use Defender XDR?
Defender XDR is usually the right starting point when your main focus is Microsoft security protection and investigation.
- You need endpoint detection and response.
- You need email and phishing protection.
- You need identity threat detection.
- You need Microsoft-native incident correlation.
- You want to investigate Microsoft 365 and endpoint activity quickly.
When should you use Sentinel?
Sentinel becomes important when you need wider SIEM, SOAR and SOC capability.
- You need third-party log ingestion.
- You need custom analytics rules.
- You need longer-term security data retention.
- You need workbooks and SOC dashboards.
- You need automation and playbooks.
- You need enterprise-wide threat hunting.
Agent Foskett investigation tip
Think of Defender XDR as the specialist investigator for Microsoft security workloads, and Sentinel as the command centre that brings evidence together from across the organisation.
Common mistake
A common mistake is saying:
“Sentinel replaces Defender.”
That is not the right way to think about it. Sentinel makes Defender data more useful by placing it inside a broader SOC workflow.
Agent Foskett takeaway
Microsoft Defender XDR tells you what is happening inside Microsoft's security ecosystem.
Microsoft Sentinel helps you understand what is happening across your entire organisation.
Related Agent Foskett learning
Microsoft Sentinel Academy progress
Microsoft Sentinel vs Microsoft Defender XDR
Microsoft Sentinel and Microsoft Defender XDR work together in Microsoft security operations. Defender XDR provides extended detection and response for Microsoft workloads, while Microsoft Sentinel provides cloud-native SIEM and SOAR across Microsoft and third-party environments.
Microsoft Sentinel Lesson 2
This Agent Foskett Microsoft Sentinel Academy lesson explains Defender XDR, Sentinel, SIEM, SOAR, third-party log ingestion, enterprise SOC operations, analytics rules, incidents, automation and threat hunting workflows.
