Land use has changed over the years tremendously in Trishal Upazila as well as throughout the country due to aquaculture and other productive purposes. Hence, the study was conducted to detect the land use change using Geographical Information Systems (GIS) and Remote Sensing (RS) images for better aquaculture planning in Trishal Upazila, Mymensingh. For this Landsat TM Image of 1999 and Google image of 2012 were collected and imported into IDRISI Kilimanjaro. Normalized Difference Vegetation Index (NDVI) was prepared using NIR, MIR and blue bands for discriminating the vegetation in the images. Cluster was also done with 5% linear stretch with 10 classes to guide the images for unsupervised classification. Later on both the NDVI and cluster images were reclassified into four land use classes as water, bare land, low vegetation and high vegetation for NDVI and bare land, water body, field crops and homestead vegetation. In the FCC images blue and blackish and purple colour represented the water colour. The other colours in all the images represented more or less the same land use phenomenon. The image interpretation showed that in the unsupervised image classification of Landsat TM image of 1999, total bare land was 212 km2 and water body was 115 km2. However, the bare land has decreased to 115 km2 from 212 km2 and the water body has increased to 74 km2 which was 8 km2 in Landsat TM image of 1999, that means bare land has decreased 28% and the water body has increased 19% which has been sporadically dug for aquaculture. By contrast, the vegetation has increased 10% in NDVI Google image of 2012 than the Landsat TM image of 1999. Therefore, it is evident that 66 Km2 (28%) of water body has increased in the 2012 Google image than the 1999 Landsat TM image, meaning land use has changed tremendously in the study area over the last fourteen years. It is also noted that vegetation has increased in the area due to water availability round the year in the region as fish ponds are everywhere. However, we have to be cautious to agricultural land conversion to fish ponds as we need also rice to feed our people and conversion will only be permitted when follow the planning rules and integration of fish with agriculture is done.