The volume of Treated Wastewater (TW) produced in Oman is increasing, due to increased connection of houses to the sewage network and increased construction of wastewater treatment plants. Despite 68% of the TW been used for irrigating urban landscapes, 10.3 Mm3 TW has been discharged to the sea in 2014. Wastewater treatment plants are owned and operated by private companies, which aspire to sell excess TW, particularly to farmers, in order to recover cost of wastewater treatment. This paper has used the Contingent Valuation Method (CVM) to estimate the farmers' Willingness to Pay (WTP) for TW for farm irrigation. Seventy two farmers responded to a face-to face interview on eliciting WTP to purchase TW as irrigation water, out of a total population of 400 farmers in Seeb region who have farms in proximity to a wastewater treatment plant. The results indicated that farmers' WTP for TW was on average 0.111 OR/m3. WTP for TW was significantly affected by the income of farmers and whether the farm is a market oriented or non-market hobby oriented farm. The percentage of farmers willing to pay the average price or higher was 38%. Most farmers are not willing to pay the price currently charged by the wastewater treatment company for landscaping irrigation (0.220 OR/m3) given the large volumes required for farm irrigation. Even rich farmers maintaining hobby farms are willing to pay only 0.128 OR/m3 versus 0.087 OR/m3 by the market oriented farmers. The WTP for TW is higher than the prices reported (OR 0.005 to 0.023 OR/ m3) for groundwater used in agriculture in Oman.