Background: International guidelines recommend that following an early-pregnancy ‘opt-out’ referral for smoking cessation support, pregnant women who smoke should also be offered referrals at subsequent antenatal appointments (‘opt-in’ referrals). We assessed feasibility and acceptability of introducing ‘opt-in’ self-referral forms to stop smoking services (SSS) in antenatal clinics. Method: A ‘before–after’ service evaluation and qualitative interviews. ‘Opt-in’ self-referral forms were distributed by reception staff to women attending antenatal ultrasound appointments. We collected hospital/SSS data for the study period and a comparison period 12 months prior. Reception staff were interviewed and data analyzed thematically. Results: Over 6500 women entered antenatal care in each period; ~15% smoked and ~50% of those who smoked were referred to SSS at their first appointment. In the study period, 17.4% of women completed ‘opt-in’ forms. Of these 17.3% smoked, and 23.1% of those who smoked requested a referral. The staff thought new procedures had minimal impact on workload, but were easy to forget. They believed the pathway would be better delivered by midwifery staff, with additional information/advice to improve engagement. Conclusions: ‘Opt-in’ referrals in later pregnancy result in significant numbers of women who smoke indicating interest in smoking cessation support. Additional training and support is necessary to motivate reception staff to oversee self-referral pen-and-paper procedures effectively.