We aimed to examine the association between low-carbohydrate diet (LCD) scores during the first trimester and gestational diabetes mellitus (GDM) risk in a Chinese population. A total of 1455 women were included in 2017. Dietary information during the first trimester was collected by 24-hour dietary recalls for 3 days. The overall, animal and plant LCD scores, which indicated adherence to different low-carbohydrate dietary patterns, were calculated. GDM was diagnosed based on the results of a 75-g, 2-h oral glucose tolerance test at 24-28 weeks gestation. Log-binomial models were used to estimate relative risks (RRs) and 95% confidence intervals (CIs). The results showed that the multivariable-adjusted RRs (95% CIs) of GDM from the lowest to the highest quartiles of the overall LCD score were 1.00 (reference), 1.15 (0.92, 1.42), 1.30 (1.06, 1.60), and 1.24 (1.01, 1.52) (P=0.026 for trend). Multivariable-adjusted RRs (95% CIs) of GDM from the lowest to the highest quartiles of the animal LCD score were 1.00 (reference), 1.20 (0.96, 1.50), 1.41 (1.14, 1.73), and 1.29 (1.04, 1.59) (P=0.002 for trend). After additional adjustment for gestational weight gain before GDM diagnosis, the association of the overall LCD score with GDM risk was non-significant, while the association of animal LCD score with GDM risk remained significant. There was no statistically significant association between the plant LCD score and the risk of GDM. In conclusion, a low-carbohydrate dietary pattern characterised by high animal fat and protein during the first trimester is associated with an increased risk of GDM in Chinese women.