Indian siris, Albizia lebbeck (L.) Benth., is a useful tree that is being widely planted for shade in the Ahwaz region of southwest Iran. The tree is, however, severely attacked by the citrus red mite Eutetranychus orientalis Klein. Seasonal population dynamics of the mite were investigated on A. lebbeck in Ahwaz during 2010–2011. Eutetranychus orientalis had two population peaks on A. lebbeck. The first and second activity periods were observed from 10 August to 28 October 2010 and 24 February to 20 June 2011, respectively. The highest density and activity of E. orientalis was observed during September to November and April to May. During these months, the average temperature and relative humidity were 20–35 °C and 21–40%, respectively. The spatial distribution of the mite was evaluated using the parameters of Taylor's power law, which revealed an aggregated spatial distribution of E. orientalis on A. lebbeck. The results of the study could be applied to develop an integrated pest management programme against the pest.