The current study investigated the relationship between children's and parents' self-reported maths affect and children's maths achievement. Participants comprised 186 child-parent dyads in Turkey. Findings showed that maths affect in children and their parents was unrelated. However, maths affect was a significant predictor of children's maths achievement. Importantly, this varied by grade. In grade three, child maths affect significantly predicted maths achievement, whereas parent maths affect was unrelated to achievement. Conversely, in grade four, the opposite pattern emerged; parent maths affect significantly predicted children's maths achievement, whereas child maths affect was unrelated to achievement. Furthermore, children's maths achievement significantly varied according to parents' level of education, whereby children whose parents were educated to undergraduate level considerably outperformed those whose parents were educated only to primary level. Parents with a lower educational status also reported significantly more difficulty in supporting their child's maths learning. These findings point towards the importance of parent maths affect, their level of education, and perceived difficulty in supporting children, as predictors of children's maths achievement. This is only the case in grade four, as maths becomes more challenging and there is a greater emphasis on competitive assessment. As such, the home numeracy environment and family maths tension should be addressed in preparation for children moving into grade four.