<![CDATA[This study examined whether Problem-Based Learning (PBL) was associated with improved mathematical creative thinking in similarity among ninth-grade students. A quantitative pre-experimental one-group pretest-posttest design was used with 22 students in Grade IX-1 at SMP Negeri 1 Sukamakmur, Aceh Besar, selected through purposive sampling. Creative thinking was assessed through four essay problems covering fluency, flexibility, originality, and elaboration. Scores were analyzed descriptively and with a paired-samples t-test after checking the normality of score differences. The mean score increased from 31.53 on the pretest to 61.51 on the posttest, a mean gain of 29.97 points. All four indicators improved, with the largest gain in fluency. The paired-samples test showed a statistically significant within-group increase, t(21) = 15.94, p < .001, with a large standardized effect, Cohen's dz = 3.40. All 22 students obtained higher numerical scores, and 21 students (95.5%) moved to a higher descriptive creativity category. These findings indicate substantial improvement after PBL implementation. However, because the study used no control group, the result should be interpreted as strong within-group evidence rather than definitive causal proof. PBL can support creative mathematical thinking by engaging students in exploring, comparing, and explaining alternative solution strategies.]]>
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