Existing research has widely accounted the influence of microblogs on traditional news production, but less attention has been paid to how microblogs are socially constructed in newsrooms. Taking the social constructivist approach, this study explored the professional and organizational construction of journalistic use of microblogs. We conducted 33 in-depth interviews with news workers at two local newspapers in China and a textual analysis of their microblog posts. We found that Chinese news workers heavily stressed professional values and journalistic authority, which set limits to information appropriation and self-expression on microblogs. Production culture, organization policy, and organization culture were also found to shape journalistic use of microblogs. The highly censored press environment restricted both organizational and individual use of microblogs, but sometimes motivated news workers to seek extra value on microblogs.