Evapotranspiration (ET) is an important method of water loss in a wetland system. Accurately estimating wetland ET and analyzing its spatial and temporal patterns are crucial. The ET estimation of eight growing seasons in the Liaohe River Delta wetland during 1985-2017 was conducted using a Surface Energy Balance Algorithm for Land (SEBAL) model with Landsat and meteorological observation data. The temporal and spatial patterns and causes of growing season ET were analyzed. Results showed the following:(1) the average relative error of the regional ET estimated by the SEBAL algorithm was 9.01%, and the correlation coefficient between the measured and estimated values was 0.61, which indicated that the estimated values were reliable. (2) The distribution of the average and relative change rate of daily ET exhibited bimodal characteristics in the study area:the lowest trough happened in 2005, whereas the crests occurred in 1989 and 2014. (3) The area of land-water junction presented the lowest ET. The high values of ET appeared in the eastern, southern, and middle parts of the region, whereas a low ET happened in the western area. The daily ET displayed a highly heterogeneous spatial distribution. (4) The ET of different land use/cover types, in descending order, was water body, wetland vegetation, non-wetland vegetation, and non-vegetation (except the water area). The characteristic across different land use/cover types from 1985 to 2017 presented a bimodal trend. The total daily ET was related to landscape transformation. The land use/cover type was a significant factor of the temporal and spatial distribution of ET. (5) The daily values of ET were significantly correlated with the corresponding weighted values of solar radiation, air temperature, wind speed, and relative humidity. The correlation coefficient was 0.69, and their annual fluctuations were relatively similar. The ET was closely related to the meteorological factor change.