This quasi-experimental research aimed to ascertain which teacher-develop biology worksheets-textual and graphical when given as additional learning materials, would give greater significant difference in students' competency level in biology. The experimental study was conducted in one of the private schools in Iloilo City using the single group of 28 second year section A high school students duly enrolled for the school year 2009-2010 and served as the research participants. The researcher-made pretest (pre-treatment) was first administered to the students. Then the experimental study was conducted for a period of six weeks to assess the research participants using the validated researcher-made biology worksheets in textual and graphical forms used as materials during the intervention to ascertain significant differences in the biology competency level of the respondents. The simple random through lottery method technique served as the basis for grouping the respondents into two groups, the textual and graphical groups. The textual group was exposed to the textual type of worksheets while the graphical group was given graphical type of worksheets. Furthermore, a researcher-made test was given again administered at the end of the treatment as posttest. To analyze the gathered data , mean and standard deviation were used as descriptive statistics to describe the biology competency level of the students. The results of the pretest and posttest were compared to evaluate the effectiveness of the worksheets in enhancing the biology competency level of the students. Furthermore, the manner by which the scores of students were interpreted was based on the Department of Education's National Testing and Research Center categorized as low performance, average performance and high performance. The results of the study revealed that the respondents had average competency level in biology before the intervention of pre-treatment and the two groups were comparable at the start. After the intervention, the posttest of the respondents attained high competency level, implying that the use of worksheets, specifically with graphics, enhanced the biology competency of the students, particularly the graphical group. On the other hand, Wilcoxon Signed Ranked Z Test for dependent sample was used to compare mean pretest scores and mean posttest scores in biology of the graphical and textual groups while Mann Whitney U Test for independent sample used to compare the pretest and posttest mean scores in biology of the textual and graphical groups set at .05 alpha level of significance was the inferential statistics. Results showed that there were no significant difference in the mean pretest scores in biology of the two groups, implying that they were comparable at the start of the study. As to the mean posttest scores and mean pretest scores in biology of the textual group, results showed that there was no significant difference; however, there was a significance difference in the mean posttest and mean pretest scores in biology of the graphical group. As to the mean gain scores in biology of the textual group and graphical groups, results revealed that the mean score of the graphical group were significantly higher than those of the textual group, indicating that the influence of the treatment introduced in the study, which was the graphical worksheets, was effective in the biology competency level of the second year high school students.