Exposure to secondhand smoke (SHS) during pregnancy can cause pregnancy complications and adverse birth outcomes. About 40% of Chinese expectant fathers are smokers and they rarely attempt to quit smoking. There is a paucity of effective smoking cessation services targeting this population. In this study, we assessed the smoking behavior of Chinese expectant fathers and examined its association with smoking abstinence after their partner became pregnant, which is an essential prerequisite for designing effective smoking cessation interventions. We conducted a cross-sectional survey in the obstetrics and gynecology clinic of three tertiary hospitals in China. Expectant fathers who smoked at least one cigarette per day for 1 month within the past 12 months were invited to participate in this study. The participants were asked to complete a structured questionnaire that assessed their smoking behaviors before and after their partner became pregnant. From December 2017 to March 2018, we recruited a total of 466 eligible expectant fathers, among whom 323 (69.3%) were identified as current smokers and 143 (30.7%) were ex-smokers. Using lasso regression, 19 features were selected from among 27 independent variables. The results of the selected multivariable logistic regression model showed that knowledge about the health hazards of smoking among smokers (odds ratio (OR) 1.39; 95% confidence interval (CI) 1.24 to 1.58; p < 0.001), knowledge about the health hazards of SHS to pregnant women (OR 1.46; 95% CI 1.09 to 1.97; p < 0.001), knowledge about harm to the fetus and newborn (OR 1.58; 95% CI 1.25 to 2.03; p < 0.001), and being a first-time expectant father (OR 2.08; 95% CI 1.02 to 3.85; p = 0.046) were significantly positively associated with smoking abstinence among expectant fathers after their partner became pregnant. Significantly negative associations were found for severe dysfunctionality in terms of family support (OR 0.48; 95% CI 0.24 to 0.95; p = 0.036) and smoking only outside the home (OR 0.81; 95% CI 0.26 to 0.98; p < 0.001). In this study, we identified several factors associated with smoking abstinence among expectant fathers after their partner became pregnant. These findings can guide the development of effective interventions targeting expectant fathers, to help them quit smoking.