Training on laparoscopic box trainer (BT) improves suturing skills in the operating room (OR). Optimal laboratory training should provide trainees with an adequate level of skills that can be transferred to the OR with no decline in performances. This study aimed to compare OR intracorporeal suturing performances of residents who trained with a fundamentals of laparoscopic surgery (FLS) BT vs. those of experienced laparoscopists. This was a prospective observational study. Residents received training with an FLS BT over a period of 4 months. Their performances with the BT and in the OR were then compared with those of experienced senior surgeons. OR assessment took place during a laparoscopic myomectomy. Performance evaluation was based on time taken and 2 validated qualitative assessment tools (GOALS and the Moorthy checklist). One academic tertiary care center, La Conception Hospital, Assistance Publique -Hopitaux de Marseille, Marseille, France, was involved. Twelve gynecology residents and 6 experienced laparoscopic surgeons. Following the FLS training period, performances of residents with the BT were equivalent to those of the experienced surgeons. When tested in the OR, the trained residents performed more slowly than experienced surgeons (279.75 vs. 159.75s; p = 0.001), and they obtained lower qualitative outcomes in terms of GOALS (13 vs. 16.75; p = 0.002) and checklist (18.25 vs. 21; p = 0.049). Transfer from the BT to the OR revealed an increase in time taken that was significantly higher for the trained residents' group than for the experienced group (137s vs. 49s; p < 0.001). A performance gap emerged between trained residents and experienced surgeons when transferring from the BT to the OR. Finding an intermediate training platform between the BT and independently suturing in the OR is hence warranted.