Background & Aims: To improve convenience and maximize flexibility whilst pumping, wearable pumps have been designed however, their performance have not been evaluated. This study aimed to develop the protocol and evaluate the efficacy and comfort of a new hands-free, in-bra, breastmilk collection pump set (IBCPS) connected to a personal use double electric breast pump. Methods: In this cross-sectional observational study 23 participants in established lactation (1–6 months postpartum) completed one pumping session with an IBCPS where both breasts were pumped simultaneously (n = 46) using the participant's maximum comfortable vacuum for a period of 15 minutes of expression after milk ejection. Milk output and removal parameters were measured together with maternal comfort. Participants completed a 24-h milk production profile to allow percentage of available milk removed (PAMR) during the pumping session to be calculated. Results: The amount of milk expressed from each breast (n = 46) was 71.7 ± 40.7 g and from both breasts combined (n = 23) was 143.3 ± 62.0 g. For each breast, PAMR was 73.6 ± 32.1 % and the rate of milk removal was 4.9 ± 2.6 g/min. Participants rated pumping with IBCPS as comfortable. Conclusions: Applying an IBCPS resulted in efficient and effective breast emptying without considerable compromise in comfort. This study has established a protocol to objectively determine the efficacy of wearable pumps.