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Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the registration statements (Nos. 333-232884, 333-237062, 333-254179, 333-263094, 333-270141, 333-270146, 333-275881, 333-277472, 333-285331, and 333-291226) on Form S-8 and in the registration statement (No. 333-277470) on Form S-3 of our report dated February 26, 2026, with respect to the consolidated financial statements of Castle Biosciences, Inc. and subsidiaries and the effectiveness of internal control over financial reporting.

/s/ KPMG LLP

Houston, Texas

February 26, 2026