Work activity is central to human psychology. However, working conditions under capitalist socioeconomic relations have been posited as psychologically alienating. Given the negative impact of work alienation on well-being and mental health, we conducted two studies of the relations between social class, work conditions, and alienation. We also examined factors that might counteract alienation – class consciousness and activism. The utility of a Marxist measure of social class – based on objective work relations – was compared with that of SES and subjective class measures. Study 1 surveyed 240 U.S. adults from diverse socioeconomic backgrounds using Amazon’s Mechanical Turk; Study 2 was a replication with 717 adults recruited via a sampling company. Across studies, alienation was predicted by perceived work exploitation, poor work relationships, and lack of self-expression, meaningfulness, self-actualization, autonomy, and intrinsic motivation at work. Only the Marxist class measure – not SES or subjective class measures – predicted alienation and alienating work conditions across studies. Working-class participants experienced more alienating work conditions and greater alienation. Alienation was correlated with class consciousness, and class consciousness was associated with activism. While SES measures have dominated the psychological study of social class, results suggest benefits to integrating Marxist measures and conceptions of social class.