In this study, based on quasi-experimental research, was investigated the effects of teaching Python programming language via Blockly tool, which had hybrid interface, on students' computer programming anxiety, cognitive load level, and achievement. Participants were 90 high school students, 44 of them in experimental group (hybrid interface) and 46 of them in control group (non-hybrid interface). According to results, there was a meaningful difference between programming achievement scores of students in favor of experimental group while there was no difference in terms of computer programming anxiety between groups. Moreover, after 10-week implementation process, students' anxiety increased in each group. It was found out cognitive load levels of both groups in the first week were higher than final week. Although both weekly and 10-week intrinsic, extraneous, germane, and total cognitive load levels of experimental group were lower than control group, there was no significantly difference between groups. Consequently, it can be said that programming via hybrid interface, using Blockly, has not an effect on students' computer programming anxiety positively whereas it helps to keep cognitive load at low level and to increase students' programming success more. It is recommended that considering these results to make computer programming education is more efficient in high schools and administrators encourage the teachers to use programming tool had hybrid interface such as Blockly.