Extract of the plant Costus speciosus was evaluated for its potential acaricidal and ovicidal activities against the two-spotted spider mite, Tetranychus urticae Koch, for the first time under laboratory conditions. The acaricidal activity was performed by studying the mortality, fecundity, fertility and offspring development of adult females at two different temperatures. The LC₅₀ value of C. speciosus is 2.3 %. Treatment significantly affected the fecundity of the females, percentage of hatched eggs, percentage of eggs reaching adult stages and duration of each life cycle stage. The acaricidal efficacy of this extract is temperature dependent. The greater susceptibility of T. urticae to C. speciosus was recorded at a lower temperature. Concerning the ovicidal activity of C. speciosus, extract exhibited 79.67 ± 4.01 % mortality on eggs. It also significantly delays the egg hatching of T. urticae compared to the control. Results showed that hatching started on the sixth day post-deposition in the treated group compared to the fourth day in the control group. All hatched eggs turned into nymphs in the control group while treatment reduced the number of hatched eggs and caused death of all hatched larvae before reaching nymphal stages. Extract of C. speciosus has promising acaricidal and ovicidal activities that could lead to the development of new bio-acaricides and is worth further investigation.