Background <p>Emerging adulthood is a developmental period associated with increased vulnerability to suicide probability due to biological, psychological, and environmental transitions. Lifestyle-related factors such as sleep regularity, chronotype, physical activity, and exposure to potentially traumatic events may be associated with mental health outcomes during this stage. However, the relative contribution of these factors to suicide probability indicators in emerging adulthood remains insufficiently understood, particularly when examined simultaneously within a multidimensional framework.</p> Methods <p>This study employed a cross-sectional survey design. Data were collected from 495 emerging adults aged 18–29 through an online questionnaire. Suicide probability and its subdimensions (hopelessness, suicidal ideation, negative self-evaluation, and hostility) were assessed using the Suicide Probability Scale (SPS). Chronotype was measured with the Morningness–Eveningness Stability Scale Improved (MESSi). Self-reported sleep regularity, exercise participation, earthquake exposure, and gender were included as categorical variables. Multiple linear regression analyses were conducted to examine the associations between these variables and overall suicide probability and its subcomponents.</p> Results <p>The findings indicated that irregular sleep patterns and lack of regular physical activity were significantly associated with higher levels of overall suicide probability and several subdimensions, including hopelessness, negative self-evaluation, and hostility (<i>p</i> &lt; .05). Participants reporting poor sleep regularity and physical inactivity reported higher levels of suicide probability indicators. In contrast, chronotype, earthquake exposure, and gender were not significantly associated with suicide probability within the present models (<i>p</i> &gt; .05).</p> Conclusions <p>The results suggest that lifestyle-related behavioral factors, particularly sleep regularity and physical activity, may be linked with suicide probability indicators during emerging adulthood. Given the cross-sectional nature of the study, these findings should be interpreted as associations rather than causal relationships. Nevertheless, the results highlight the potential relevance of routine-based behavioral factors for suicide probability prevention strategies. Universities and community mental health services may consider incorporating low-cost preventive initiatives, such as sleep hygiene education and the promotion of regular physical activity, within broader mental health support programs for young adults.</p>