This study contributes to research in the field of phonology of sign languages, focusing on the occurrence of assimilation of signs. The objective of the study is to analyze assimilation cases present in the text genre "joke" in Brazilian Sign Language (Libras), as well as influences of the immediate context on their occurrence. We understand that assimilation occurs when one unit takes features from another unit next to it (Liddell and Johnson 1989; Valli et al. 2011; Resende 2012). Thus, four jokes were selected from the YouTube video platform and signs that show the process of assimilation were selected to constitute our corpus. The data were analyzed qualitatively. Based on the corpus and on the analyses, we found that the tendency, in the four jokes in Libras that we investigated, is that one-hand signs affect one-hand signs in a progressive and strong way. Therefore, we conclude that it is possible to hypothesize that assimilation occurs as a principle of linguistic economy, considering that the sign unit that is assimilated into the other would be very distant from the unit (previous or subsequent) of the sign, which would be antieconomic.