•Testosterone is associated with patient reported sexual outcomes among HNC patients.•It is estimated that 10-25% of HNC patients may have testosterone insufficiency.•Further research is warranted to investigate possible causes of sexual problems. To investigate associations between testosterone and patient reported sexual problems and need for sexual care in head and neck cancer patients at time of diagnosis and 6 months after treatment. Data and samples were used of 40 patients (20 men, 20 women) before and 6 months after treatment. Outcome measures were total testosterone level (TT) and free testosterone index (FTI), testosterone insufficiency (TI), the EORTC QLQ-HN35 Sexuality subscale, the subscales of the International Index of Erectile Function (IIEF), Female Sexual Function Index (FSFI), and the Sexuality subscale of the Short-Form Supportive Care Needs Survey (SCNS-SF34). In men, higher FTI before treatment was significantly associated with better IIEF Orgasm (p = 0.020) and at 6 months follow-up with IIEF Desire (p = 0.019). Before treatment, insufficient testosterone was present in 5 males (25%) and in 3 at follow-up (15%) (2 patients who had TI before treatment plus one). In women, higher TT at follow-up was significantly associated with better EORTC Sexuality (p = 0.031) and FSFI Satisfaction (p = 0.020); FTI at follow-up was associated with FSFI Satisfaction (p = 0.012). Before treatment, TI was present in 2 women (10%) and in 3 (15%) at follow-up (the same 2 patients plus one). This pilot study showed that testosterone seems to be associated with patient reported sexual outcomes among male and female head and neck cancer patients. It is estimated that 10–25% of HNC patients may have testosterone insufficiency before treatment and/or at 6 months after treatment.