In Laos, smallholder cattle farmers rely primarily on natural grassland grazing, which needs to be improved for fattening. Notably, most cattle prices are determined by the middleman, by looking, so buyers tend to undervalue their price, which makes cattle farming a minimal investment. Urea-Molasses Block (UMB) supplements can effectively enhance a nutrient diet in low-quality roughage systems. This study aimed to determine factors affecting UMB and farmers’ Willing To Pay (WTP) for UMB as a new input material with data from six villages, two districts of the Vientiane Capital, in January and July 2019. The results indicate that farmers with relatively high education, consent to the positive effect of UMB, and previous experience purchasing feed during the dry season are more likely to pay a high positive WTP. The average WTP for UMB ranges from USD 5.7 to 6.5 per month for one cattle, which is approximately 10.2~11.6% of current annual costs for average smallholder cattle farmers. These findings will be significant in improving productivity at the initial development stage of farms in Laos, especially for smallholder farmers.