This study aimed to explore the relationship between mathematics anxiety and mathematics achievement of Grade 10 students across gender in 6 government girls' secondary schools and 6 government boys' secondary schools in District Khairpur Mirs', Sindh. This study focused on three main themes: (1) gender differences in mathematics anxiety; (2) gender differences in mathematics achievement; (3) relationship of mathematics anxiety with mathematics achievement across gender. Data were collected in two phases. In the first phase, data were collected through an adapted (Cavanagh & Sparrow, 2011), piloted and modified Mathematics Anxiety Rating Scale (MARS). MARS used a five-point Likert scale. The total sample size for the first phase was 309 students, that comprised males (n= 173) and females (n= 136). MARS indicated that students of both the genders exhibited almost equal overall mathematics anxiety with a slight difference which was not significant. Moreover, males showed a significantly high level of attitudinal anxiety as compared to females, whereas, female students showed a significantly high level of cognitive anxiety as compared to males. Data for mathematics achievement was collected through a Mathematics Achievement Test (MAT), which was developed from past four-year annual examination papers for science group of Board of the Intermediate and Secondary Education, Sukkur. There were 25 Multiple Choice Questions (MCQs) and 10 Constructed Response Questions (CRQs). MAT was conducted with a sample of 264 Grade 10 students in the same schools where MARS was conducted. MAT showed that male students performed significantly better than females in CRQs and MCQs. Male students have also significantly outperformed females in overall mathematics achievement. This study did not indicate that low mathematics achievement is because of mathematics anxiety. However, female students have high level of mathematics cognitive anxiety, which might have negatively influenced their mathematics achievement. Overall mathematics achievement of the whole sample (M = 12.92) is a point of concern. This study makes an important contribution to the existing research literature from Pakistan especially related to the rural context.