The present study aimed at the effect of concept mapping strategies on learners’ achievement and retention in biology teaching. A pretest/posttest quasi-experimental research design was adopted with one control and experimental group. The target population was male students who studied in second grade of high school in 2023-22 educational year in Iran. Simple random sampling technique was used to select the sample of students. Considering the Cohen tables and statistical assumptions, a sample size of 40 participants was estimated. They were then randomly assigned to each group. The experimental group made use of concept mapping strategies, while the control group was taught using the traditional methods. An academic achievement teacher made test was administered to all groups as a pretest / posttest and biology achievement retention teacher made test, a separate delayed posttest was administered after three weeks to the learners of the groups. The obtained data were analyzed using one-way Ancova test. The results indicated that concept mapping strategies had a significant effect on learners’ achievement. Analysis of the data using t-tests revealed that the retention of biology teaching by using concept mapping strategies was significantly higher in comparison to the traditional methods.