This study aimed to explore the effectiveness of Teasdale cognitive therapy (based on mindfulness) on the reduction of anxiety, stress and depression among pregnant woman aged fewer than 20.Methods This study method was pre-posttest with control group and the study population included all pregnant women of Ardebil who was below 20 and suffering from anxiety, stress or depression during the year 2013. The selected sample comprised 30 below 20 age pregnant women who selected by convenience method and assigned randomly in control and experimental group. The data collected by anxiety, stress and depression questionnaire and trait anxiety questionnaire of also used to measure the anxiety. The collected data analysed by Multiple Analysis of Variance (MANOVA). Results, The result of MANOVA revealed that mindfulness based cognitive therapy significantly is effective on stress, anxiety and depression of pregnant women who aged below 20. Conclusion, According to the findings of this study and other relevant studies as pregnancy is a very sensitive stage of every woman's life and they need proper care. The authors suggest to future researchers to design and explore MBCT based on pregnancy condition associated problems.