Introduction Currently, abortions are significant public health concerns among Thai adolescents. Therefore, investigating the factors that predict the intention for abortion in this population is crucial, contributing to the development of guidelines aimed at preventing abortions among Thai adolescents. Objective The aim of this study was to examine factors predicting abortion in adolescents. Design This study employed a correlational predictive design, applying the Theory of Planned Behavior. Methodology Through purposive sampling, the participants consisted of 120 adolescents aged 13–19 years residing in Bangkok. Sample size was determined based on Green statistics. The research instruments included questionnaires on attitudes toward abortion, subjective norms about abortion, perceived control for abortion decision-making, and intention for abortion. Content validity was examined by five experts, obtaining the content validity indices (CVIs) of 1.00, 1.00, .96, and 1.00, respectively. Reliability was tested, yielding Cronbach’s alpha coefficients of .74, .84, .68, and .93, respectively. Data were collected through self administration between October 2021 and March 2022. Data were then analyzed using descriptive statistics and Multiple Regression Analysis. Results Participants had mean age of 13.95 years (SD=1.70). Multiple regression analysis showed that the participants’ attitudes toward abortion and perceived control for abortion decision-making jointly accounted for 42.4% of the variance in adolescents’ intentions for abortion (F = 28.486, p < .001). Perceived control for abortion decision-making had the highest predictive power (β = −.419, p < .001), followed by attitudes toward abortion (β = −.252, p = .002). However, subjec- tive norms about abortion did not significantly predict intention for abortion. Recommendation Efforts should be made to develop a program for adolescents experiencing unwanted pregnancies to foster positive attitudes towards preventing abortion and perceived control for abortion decision-making that will mitigate intention for illegal abortion.