Purpose Vastus lateralis (VL) can be used to reconstruct defects of the head and neck. Whilst the advantages are documented, donor-site morbidity is not well described. This study aimed to assess donor-site morbidity after VL flap harvest. Results will determine future directions for preventative and post-operative care to improve patient health outcomes. Methods Ten participants (mean age 55 years) were assessed for the presence of donor-site morbidity after VL harvest. Musculoskeletal (pain, muscle strength, muscle length and tactile sensation), quality of life (SF-12), lower extremity function, gait (function and speed) and sit-to-stand were assessed using validated and standardized procedures. The outcomes were compared to age-matched healthy reference values or the non-operative side. Analyses were conducted using descriptive statistics and non-parametric tests. Results There was no difference in muscle strength (knee extension), muscle length, ability to sit-to-stand, or gait function (all P > 0.05). Knee flexor muscle strength was significantly less on the operated leg compared to the non-operated leg (P = 0.02) and walking speed was slower than age-matched healthy values (P < 0.001). Thigh tactile sensation was impaired in 89% of participants. Quality of life was significantly less for the physical health component of the SF-12 (P < 0.001). The mental health component of the SF-12 was similar to healthy controls (P = 0.256). Conclusion There was no effect on donor site morbidity with regards to knee extensor strength, pain, walking function, ability to sit-to-stand and muscle length. VL harvest affected donor-site knee flexion strength, walking speed, tactile sensation and physical health-related quality of life.