Many head and neck cancer (HNC) survivors experience reduced quality of life due to radiotherapy (RT)-related dysphagia. The aim of this prospective randomized trial was to evaluate the impact of prophylactic swallowing exercises on swallowing-related outcomes in HNC patients treated with curative RT. Patients treated with primary RT for HNC were candidates for this randomized protocol. Participants in the exercise group were instructed to perform swallowing exercises at home. Participants in the control group were given standard care. Patients were evaluated with modified barium swallow and several other secondary outcome measures at four and nine different time points, respectively. Data were analyzed according to intention-to-treat analyses. A total of 44 consecutive patients were included; 22 in each group. In general, there was no difference between the two groups regarding any of the dysphagia outcomes during and after treatment. Adherence to exercises was poor and dropouts due to especially fatigue were very frequent in both groups. Systematic swallowing exercises had no impact on swallowing outcomes within the first year after RT. Despite repeated supervised sessions, adherence to exercises was a major issue and dropouts were frequent in both the intervention and control group.