The persistent decline in academic achievement of senior secondary school students in Biology, particularly in Cross River State, has become a pressing concern for educators, parents, and policymakers. It is on the ground of this concern that the study sort to investigate the influence of self-concept and study habits on Senior Secondary Student's academic achievement in Biology in Calabar Education Zone of Cross River State. Two research questions were formulated to guide the study and ex-post facto research design was adopted. The population of the study comprised all Senior Secondary School two (SS2) Biology students with a total of 16,104 and a sample size of 433 using multi-stage sample technique. Two instruments were used for data collection namely: a questionnaire titled Students' Variables Questionnaire (SVQ) and an achievement test tagged "Biology Achievement Test (BAT). While the SVQ was constructed by the researcher, the BAT was adapted from WAEC past questions in Biology. The instruments were validated by three experts, one from measurement and evaluation and two from Biology education, University of Calabar. The reliability coefficient obtained were 0.93and 0.80 using Kuder Richardson's formula. All the research questions and hypotheses were tested at .05 level of significance. The statistical tools used for research questions was Multiple correlation coefficient and hypotheses were, Pearson product Moment correlation, One-way Analysis of Variance (ANOVA). From the findings, there was a negative but statistically non-significant relationship between students' self-concept and their academic achievement in Biology, leading to the null hypothesis being retained. Based on the findings, it was concluded that while self-concept alone showed a negligible or non-significant relationship with academic achievement in Biology among others. The study further recommended among others that Enhancing students' self-efficacy are crucial, given its significant relationship with academic achievement in Biology.