ABSTRACT The vermiculated sailfin catfish ( Pterygoplichthys disjunctivus ), an invasive species, has rapidly proliferated in Bangladesh's freshwater ecosystems, threatening native biodiversity. This study examined its morphometric traits, length–weight dynamics, condition factors and relative weight over a one‐year period (August 2023–July 2024) in the Buriganga River to support management interventions. A total of 360 individuals were measured for 21 morphometric traits, and 3888 specimens were analysed for length–weight relationship (LWR), length–length relationship (LLR) and condition indices, including Fulton's condition factor ( K F ), allometric condition factor ( K A ), relative condition factor ( K R ) and relative weight ( W R ). Observed total length ranged from 4.5 to 46.2 cm, standard length from 3.2 to 39.5 cm, fork length from 4.1 to 43.8 cm and body weight from 1.04 to 1013 g—the highest weight recorded for this species in South Asia. The LWR showed positive allometric growth (pooled b  = 3.04; range = 2.78–3.08), with strong correlations in LLRs ( r 2 = 0.988–0.995). Condition indices varied significantly by month: K F (0.4230–1.8224; mean ± SD = 0.8496 ± 0.1189), K A (0.0045–0.0460; 0.0191 ± 0.0039), K R (0.5390–2.4477; 1.0114 ± 0.1187) and W R (53.8981–244.7696; 101.3785 ± 11.8748). One‐way ANOVA followed by Tukey's HSD revealed strong seasonal effects— K F ( F = 120.76, p < 0.001) and K A ( F = 2732.50, p < 0.001) were lowest during October–January and peaked in August, while K R and W R also differed significantly ( p < 0.001) with milder fluctuations. The highest condition levels observed in August reflect favourable feeding and growth conditions during the monsoon, whereas reduced winter values suggest environmental or physiological stress. These findings reveal the species’ high adaptability and physiological resilience, offering critical baseline data for designing seasonally targeted management strategies. August, identified as the peak condition period, may offer optimal timing for control interventions to reduce the ecological impact of this invasive species.