The aim of this study is two-fold: first, it is aimed to define how pre-service teachers plan and implement their lessons based upon constructivist theory; and second, to identify what kind of problems they encounter in order to help them enhance their implementations towards constructivist-orientation by assisting them in overcoming these difficulties via delivered training. The study is designed as an action research with the participation of two pre-service teachers taking “Teaching Practice” course. Data was gathered through document analysis, interviews and observation and analysed using descriptive statistics. According to the findings, participants have lack of knowledge on using teaching programs at the beginning of the study. Although they were aware of the importance of misconceptions, they ignored students’ possible misconceptions during planning and practice. Furthermore it was found that they frequently preferred teacher-centred teaching methods and techniques. Following the training, participants were observed to have overcome most of the difficulties. According to results of the study, pre-service teachers’ planning and teaching skills and knowledge about constructivist theory have improved. The findings suggest that teacher training programs need to include implementation-oriented teaching practices while providing room for teacher trainees to voice and discuss the problems they encounter during these practices.