A healthy postpartum lifestyle is vital for the promotion of optimal maternal health, return to pre-pregnancy weight and prevention of postpartum weight retention, but barriers exist. We performed a systematic review that aimed to describe the barriers and facilitators to a healthy lifestyle in the first 2 years postpartum from the perspectives of women and healthcare providers. Databases were searched for eligible studies published up to 26 August 2019. Following thematic analysis, identified themes were mapped to the Theoretical Domains Framework and the Capability, Opportunity, Motivation and Behaviour model. We included 28 qualitative and quantitative studies after screening 15,643 citations and 246 full texts. We identified barriers and facilitators relating to capability (e.g., lack of knowledge regarding benefits of lifestyle behaviours; limitations in healthcare providers' skills in providing lifestyle support), opportunity (e.g., social support from partners, family, friends and healthcare providers; childcare needs) and motivation (e.g., identifying benefits of exercise and perception of personal health; enjoyment of the activity or food). We suggest intervention components to include in lifestyle interventions for postpartum women based on the identified themes. Our findings provide evidence to inform the development of interventions to support postpartum women in adopting and maintaining a healthy lifestyle.