The increasing penetration level of renewable generation in power systems leads to challenges in frequency stability due to system inertia reduction. This study investigates the potential of the district heating system (DHS) integrated with the variable-speed heat pump to provide demand-side frequency response services while meeting end-user heating demands. Dynamic models are developed considering the thermal inertia of the DHS with the heat pump, and the dynamic performance is analyzed under rotational speed disturbances. The demand-side frequency control is proposed which regulates the supply water temperature setpoint to adjust heat pump power consumption during primary and secondary frequency response processes. The effectiveness of the proposed control is validated through a town-level case study. Results show that the proposed control effectively reduces the frequency nadir and accelerates frequency recovery, particularly under large load disturbances. For a step load increase of 0.25 p.u., the frequency nadir improves from − 0.0265 p.u. to − 0.0241 p.u and the frequency settling time decreases from 973.2 s to 913.7 s. Additionally, the room temperature variation is less than 0.8 ℃ taking 2000 s, satisfying the acceptable thermal comfort criteria.