Men who scored below average in the self-reported study tended to make 18 percent more than their nice counterparts -- approximately $9,722 more in income per year.
"Nice guys are getting the shaft," said Beth A. Livingston, an assistant professor of human resource studies at Cornell University's School of Industrial and Labor Relations, to the Wall Street Journal.
The study, entitled "Do Nice Guys and Gals Really Finish Last?" analyzed 20 years' worth of data of more than 10,000 workers. The survey factored in age, income, and profession while measuring agreeableness in a few different ways.
Women also tended to make more when scoring poorly in the agreeable scale, but less so than men. Women made about 5 percent, or $1,828, more than high scoring women on the agreeable scale.
Most companies don't even realize they are rewarding bad behavior, says the study's co-author.
"The problem is, many managers often don't realize they reward disagreeableness," says Dr. Livingston. "You can say this is what you value as a company, but your compensation system may not really reflect that, especially if you leave compensation decisions to individual managers."