The purpose of the study is to determine the effects of pre-service science teachers. scientific process and critical thinking skills on the Predict-Observation-Explain and Inquiry based strategies that have been applied to Science Education first grade pre-teachers at the General Physics-I Laboratory. In this study, the sample consists of the Science Education Department students that attended Physics-I Laboratory course during 2013-2014 Fall Semester at Istanbul University. The sample consists of 46 female and 9 male in total 55 pre-service teachers. The study"s experimental groups. were assigned randomly and experimental group-1 contained 27, experimental group-2 contained 28 pre-service teachers. In the study, pretest-posttest without control group experimental design was used. In the study, Predict-Observation-Explain strategy was applied to experimental group-1 and Inquiry based strategy was applied to experimental group-2. In order to determine the effects of each strategy on pre-service teachers. critical thinking, California Critical Thinking Disposition Inventory was used. In order to determine the effects of each strategy on pre-service teachers. scientific process skills, Scientific Process Skill Inventory was used. The inventories were applied to pre-service teachers as pre and posttests. Quantitative data were analyzed via SPSS.18 package program in digital platform. Descriptive statistics, independent sample t-test, paired sample t-test, one way variance analysis (Anova) were used to analyze quantitative data, Tukey HSD was used to define the sources of sub-dimensions. significant differences.