The tenuipalpid mites are worldwide in distribution and include several economically important pest species, about 30 genera and over 600 mite species of tenuipalpid have been described, primary in the most economically importance Tenuipalpus about 200 mite species. The flat mite, Tenuipalpus eriophyoides Baker was recorded for the first time in Egypt, whereas female and male were re-description. This mite species infesting date palm trees on the underside of leaflets in moderate numbers causing, extensive yellowing of lower leaves may be symptomatic of either –flat palm mite T. eriophyoides feeding or any of several pests or disease of palms. In this respect, biological and ecological studies were carried out to know different developmental stages and fecundity when reared on date palm leaflets Zaghloul variety under laboratory conditions. Seasonal abundance of the flat mite, T. eriophyoides infesting date palm Zaghloul and Sewi varieties in Sohag Governorate, along two seasons 2015 and 2016. Obtained data cleared that the T. eriophyoides passed through egg, larva and two nymphal stages before reaching adult. The average length of the egg stage is (13.5 & 11.2) and (11.2& 10.8 days) for female and male at 20°C and 30°C when mite reared on Zaghloul variety leaflets. 15.72 to 22.5 eggs were laid in 18.5 and 15.0 days with a daily rate of 0.85 and 1.5 eggs in the same trend. The life span lasted (63.1 & 43.7) and (44.9 & 34.3 days) for female and male, when they fed on leaflets of date palm, Zaghloul variety at 20°C and 30°C.The occurrence and seasonal abundance of the flat spider mite T. eriophyoides infesting data palm trees, zaghloul and Sewi varieties was investigated during the period from May to mid Nov. in 2015 and 2016. The population started in few numbers in May, then increased to its, peak in August on both varieties, also, data showed that Sewi variety had the higher infestation than zaghloul variety. In general season 2016 was high level infestation than season 2015, due to climatic factors.