SummaryHealthy lifestyle behaviors during the preconception period are important to optimize maternal and child outcomes, including weight. However, the majority of women do not have optimal preconception lifestyle behaviors. This systematic review explored enablers and barriers to women's preconception lifestyle behaviors using the Capability, Opportunity, Motivation, Behaviour (COM‐B) model and Theoretical Domains Framework (TDF). Preconception was defined as the time before conception, capturing planned and unplanned pregnancies. Medline Complete, EMBASE, PsycINFO, and CINAHL were searched for peer‐reviewed, quantitative and qualitative primary studies (English, 2006–2020) that explored enablers and barriers to lifestyle behaviors (diet, physical activity, smoking, alcohol use, supplement intake). Forty‐two studies (of 3406) were included, assessing supplement use (n = 37), diet (n = 10), smoking (n = 10), alcohol use (n = 8), and physical activity (n = 5). All three COM‐B components were identified only for diet and supplement use. Of the 14 TDF domains, 7 were identified: knowledge, beliefs about capabilities, beliefs about consequences, goals, intentions, social support, and environmental context and resources. The presence/absence of knowledge on healthy behaviors was the most commonly assessed enabler/barrier. Future studies should explore a wider range of factors influencing preconception women's capability, opportunity, and motivation to modify their lifestyle behaviors.