In this pilot study, we report on the feasibility, acceptability and potential impact of 'Who, When, How to Share', a new disclosure decision-making programme for autistic adults. We evaluated this programme using pre-post mixed-methods surveys that included questions about participants' experiences of the programme and four psychosocial outcome measures. While 32 autistic adults completed the pre-programme survey and enrolled into the programme, there was high attrition, with only 19 autistic adults completing the programme and post-programme survey. We found that it was feasible to deliver the programme in a guided self-help format, although a minority of participants (who completed the programme or provided reasons for withdrawing from the programme) found it challenging to work through the programme independently and within the study time frame. High levels of satisfaction and positive qualitative feedback also suggested that the programme was acceptable to autistic adults. Participants provided useful recommendations for improvement, such as more interactive elements to enhance engagement. The programme showed potential to improve decisional conflict, disclosure-related distress, stigma-related stress and internalised stigma among autistic adults, though further evaluation of the impact of the programme is needed.