Through longitudinal analysis from the GLOWING cohort study, we examined the independent and joint relationships between couples’ eating behaviors and gestational weight gain (GWG). Pregnant persons (n = 218) and their non-pregnant partners (n = 157) completed an Eating Inventory. GWG was calculated as gestation weight at 36 weeks minus that at 10 weeks. General linear models were used to examine the relationships between GWG and the pregnant persons, non-pregnant partners, and couples (n = 137; mean of pregnant persons and non-pregnant partners) cognitive restraint (range 0–21), dietary disinhibition (range 0–18), and perceived hunger (range 0–14), with higher scores reflecting poorer eating behaviors. The adjusted models included race/ethnicity, education, income, marital status, and age. The pregnant persons and their non-pregnant partners’ cognitive restraint, dietary disinhibition, and perceived hunger scores were 9.8 ± 4.7, 4.8 ± 3.2, and 4.4 ± 2.5 and 6.6 ± 4.6, 5.4 ± 3.4, and 4.7 ± 3.2, respectively. Higher cognitive restraint scores among the pregnant persons and couples were positively associated with GWG (p ≤ 0.04 for both). Stratified analyses revealed this was significant for the pregnant persons with overweight (p ≤ 0.04). The non-pregnant partners’ eating behaviors alone were not significantly associated with GWG (p ≥ 0.31 for all). The other explored relationships between GWG and the couples’ eating behaviors were insignificant (p ≥ 0.12 for all). Among the pregnant persons and couples, reduced GWG may be achieved with higher levels of restrained eating. Involving non-pregnant partners in programs to optimize GWG may be beneficial.