Ionis Pharmaceuticals (IONS) S-8Registration of securities for employees

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in the Registration Statement (Form S-8) pertaining to the Ionis Pharmaceuticals, Inc. 2020 Equity Incentive Plan of Ionis Pharmaceuticals, Inc. of our reports dated March 2, 2020, with respect to the consolidated financial statements of Ionis Pharmaceuticals, Inc. and the effectiveness of internal control over financial reporting of Ionis Pharmaceuticals, Inc. included in its Annual Report (Form 10-K) for the year ended December 31, 2019, filed with the Securities and Exchange Commission.