An experiment was conducted to study the effect of time of operation and rooting media on the rooting success of air-layering in guava at the Germplasm Centre, Fruit Tree Improvement Project, Bangladesh Agricultural University, Mymensingh during March to August, 2011. The experiment comprised of five operation times (March, April, May, June and July 2011) and 11 rooting media (50% cow dung + 50% loamy soil), (50% cow dung + 50% saw dust), (50% compost + 50% loamy soil), (50% cow dung + 50% coconut coir), 100% cow dung, 100% loamy soil, 100% compost, 100% moss, (25% cow dung + 75% loamy soil), (25% loamy soil + 75% cow dung) and 100% saw dust. The result of the experiment indicates that the effect of time and rooting media on percent rooting success, root number and root length was significant. The highest percentage of rooting success (96.97%), number of roots/layer (7.76) and length of longest root (6.17 cm) was recorded in June and lowest percentage of rooting success (58.78%), number of roots/layer (1.25) and length of longest root (1.99 cm) in July. The highest percentage of rooting success (85.33%), number of roots/layer (6.04) and length of longest root (5.43 cm) was obtained from compost and lowest percentage of rooting success (65.33%), number of roots/layer (2.29) and length of longest root (1.96 cm) was obtained from saw dust. In case of combined effect of time and rooting media the maximum rooting success (100%) was observed in the combinations of May × compost, May × moss, June × compost and June × moss and lowest (46.670%) in the combinations of July × saw dust and April × saw dust. The highest number of roots/layer (9.930) and length of longest root (9.000 cm) was obtained from June × compost and lowest number of roots/layer (1.000) and length of longest root (0.970 cm) was obtained from July × saw dust combination.