A dose setting mechanism for a drug delivery device includes a primary drug delivery assembly and a secondary drug delivery assembly. The dose setting mechanism includes a primary dose dial component for setting a dose in the primary drug delivery assembly and a secondary dose dial component for setting a dose in the secondary drug delivery assembly. The primary dose dial component and the secondary dose dial component are configured to rotate during dose setting. A gear mechanism is configured such that in a first phase of the dose setting, rotation of the primary dose dial component is transferred to the secondary dose dial component and such that in a second phase of the dose setting, the secondary dose dial component is decoupled from the primary dose dial component such that rotation of the primary dose dial component is prevented from being transferred to the secondary dose dial component.