The feasibility and efficacy of an additional progressive home-based strengthening exercise program (PHSEP) on subjects that already attended supervised institutional exercise therapy was investigated. Thirty-six hip patients with hip osteoarthritis (OA) and/or total hip replacement in at least one hip joint were randomly assigned to an intervention group (IG) or a control group (CG). IG (18 patients, mean age 64.9, standard deviation (SD) 7.5) followed an 8-week PHSEP in addition to their weekly institutional exercise therapy, while CG (18 patients, mean age 64.7, SD 9) solely continued the weekly institutional exercise sessions. Before and after the intervention period, strength of hip muscles was quantified applying isokinetic concentric and isometric measurements, and health-related quality of life was monitored using the SF36 questionnaire. Adherence to the exercise program was evaluated using exercise logs. The PHSEP was feasible for all subjects in IG with an adherence of 99%. Exercise logs reported that pain resulting from the PHSEP was low. Increased strength in isokinetic concentric hip adduction (13%) and isometric hip abduction (9%), adduction (12%), and flexion (7%) was found in IG in comparison to CG. The results of the SF36 did not change during the intervention period. Consequently, supervised institutional exercise therapy supplemented by a PHSEP could increase hip muscle strength in patients with hip OA and/or total hip replacement. However, further research should evaluate the optimal frequency and duration of such supplementary sessions and their potential to increase physical function and reduce pain.