Understanding the association of fish recruitment and flow is necessary in the management of regulated rivers in coastal regions of Australia where there is increasing human demand for water. This study compares fish assemblages and recruitment in two regulated and two nearby unregulated tributaries of the Hunter River sampled monthly using sweep net electrofishing between August 2006 and June 2007. The regulated tributaries have fewer small pulses or ‘freshes’ throughout the year compared to the unregulated tributaries, although large floods still occur at similar frequencies. I predict that these changes in the flow regime will affect both the timing and success of fish spawning, thereby influencing fish assemblages. Flow regulation did not affect fish assemblages during spawning, but appeared to influence post-spawning recruitment. Peak spawning of two abundant species, Australian smelt (Retropinna semoni) and Cox’s gudgeon (Gobiomorphus coxii), was delayed in regulated tributaries compared to unregulated tributaries. Potential mechanisms underlying these patterns include reduced parental fitness and/or delayed maturity due to altered availability of prey or changes to water temperature downstream of dams. Outcomes of this study will have implications for the development of environmental flows in coastal rivers of temperate Australia where flow regimes continue to be regulated.