Purpose <p>Preterm poses substantial physical and psychological burdens on parents. Peer support could alleviate such burdens. However, longitudinal evidence on the trajectory patterns of peer support needs among parents of preterm infants, as well as how demographic-socioeconomic characteristics influence these patterns, remains limited.</p> Methods <p>This longitudinal study recruited 76 parents of preterm infants from three tertiary hospitals in Shanghai, China. Participants completed the Peer Support Needs Scale for Parents of Preterm Infants at four key time points from birth to two weeks post-discharge. Conditional Latent Class Growth Modeling was used to identify distinct trajectory patterns of peer support needs. Parental demographic-socioeconomic characteristics were included as covariates to assess their influence on trajectory group membership. Descriptive and univariate analyses were also conducted, and model fitting was evaluated through multiple fit indices.</p> Results <p>Participants were categorized into three distinct trajectory groups based on the overall longitudinal patterns of change in their peer support needs across all time points: High-level Stable (22.37%), Moderate-level Slowly Declining (67.11%), and Low-level Rapidly Declining (10.53%). Parents with higher age and financial difficulties were more likely to be classified into the High-level Stable Group (OR = 10.72, <i>P</i> = 0.003; OR = 5.86, <i>P</i> = 0.024) or the Moderate-level Slowly Declining Group (OR = 7.71, <i>P</i> = 0.009; OR = 4.08, <i>P</i> = 0.046).</p> Conclusions <p>These findings reveal that peer support needs among parents of preterm infants are dynamic and heterogeneous. Parental age and financial difficulties among demographic-socioeconomic factors could influence peer support needs. Stage-specific, tailored peer support should be provided based on individual characteristics.</p>