Studies were conducted to improve the production of murine ascites with monoclonal antibodies that recognize SARS-CoV-2 proteins. BALB/c mice were primed with 0.5 mL of mineral oil into the abdominal cavity. Seven days after priming, mice were divided in two groups: the group 1 was inoculated intraperitoneally with 2x106 cells/mL of MAb-secreting hybridomas against the nucleocapsid and spike proteins of SARS-CoV-2; the group 2 was injected simultaneously with the same inoculum of hybridoma cells and mineral oil, 18 days after priming. No disturbances or suffering signals were observed in mice from both groups, suggesting that double administration of mineral oil did not produce significant distress with respect to the single dose used for priming, and that none of the hybridoma cell lines were particularly aggressive for the inoculated mice. Ascites was collected in 90.48% and 97.68% of mice from groups 1 and 2, respectively. Ascites was not collected in 7.42% of all mice. The main cause was they never developed ascites tumors but no solid tumors were observed either. The volume of ascitic fluid per mouse was increased significantly in mice from group 2, and there were no significant differences between groups in terms of the concentration of IgG in clarified ascites. According to these results, to obtain higher amounts of MAb the strategy applied in group 2 should be used, since it showed the best results in the development of ascites tumors and it significantly increased the volume of ascites fluid per mouse. This could allow the use of fewer animals for ascites production, which is an ethical and economic benefit.