Asian farmers often use Nitrogen (N) fertilizer inefficiently, although it is essential in rice for high yield and profit. We modified the generic recommendation of LCC use for Bangladesh condition and evaluated Leaf Color Chart (LCC) as a simple tool for managing N fertilizer in lowland rice for increased yield and profit through farmer participatory approach in farmers' fields of southwestern Bangladesh. Use of the LCC for N management consistently increased grain yield and profit as compared with farmers' N management practice across the 4 wet (Aman) and 4 dry (Boro) season in altogether 200 farmers' fields in 10 villages. Nitrogen management through use of the LCC without any other change in farmers' practice for crop and fertilizer management increased average grain yield by 0.1 to 0.8 Mg ha¹ across villages and seasons. This yield increase corresponded to a median added net return of US$40 ha¹. These positive results encourage both Government and non-Government extension service providers to take the LCC technology to the farmers throughout Bangladesh. We provided training on LCC use along with user guidelines as leaflet to 500 lead farmers, and 100 village level extension workers. Attempts are being made to manufacture locally in Bangladesh an LCC with standardized color to ensure uniformity of the critical LCC value among all LCCs available to farmers. Development of trainer group among extension people and an extensive training program on LCC use for farmers and village level extension workers are needed to scale up the LCC technology in Bangladesh.