The brain is rich in long-chain PUFA, which play an essential role in its development and functions. Here, we examined the impact of maternal n-3 PUFA intake deficiency during gestation and lactation on the development of glial cells in the pup’s developing cerebral cortex. In addition, using myelination as indicator and the anti-myelin basic protein as measurement to establish the relationship between the number of glial fibrillary acidic protein (GFAP)-positive cells and the development of oligodendrocytes, we determined the myelination state of the somatosensory cortex at postnatal day 14. Rat dams were fed either a control (Cont) or an n-3 PUFA-deficient (Def) diet for 60 d (acclimatisation: 14 d; gestation: 21 d; and lactation: 21 d). Pups lactated from dams throughout the experiment. The distribution pattern of astrocytes in pups on postnatal day 7 was immunohistochemically analysed using GFAP and brain lipid binding protein (BLBP) as markers for mature astrocytes and astrocyte-specific radial glial cells, respectively. It was observed that, when compared with Cont pups, GFAP-positive cells decreased, BLBP-positive cells increased and myelinated structures were sparser in the somatosensory cortices of Def pups. In the open field test on postnatal day 21, behavioural parameters did not differ between groups. Our results indicated that inhibited maturation of astrocytes caused by maternal n-3 PUFA deficiency hindered the development of brain glial cells of neonatal rats; hence, maternal n-3 PUFA intake during the gestation and lactation periods may have been crucial for the brain cell composition of pups.