Objective Providing appropriate health information to patients with systemic lupus erythematosus (SLE) is advantageous in the treatment decision-making process. We aimed to investigate how online health information-seeking behaviors affect shared decision-making (SDM) in patients with SLE. Methods This cross-sectional study included 464 patients with SLE from five institutions. The main exposure was time spent on the internet per day, divided into four categories (none, <1 h, 1– < 2 h, ≥2 h). Participants categorized their preferred first source of health information as physicians, the internet, or other media. The outcome was the degree of SDM measured via the 9-item Shared Decision-Making Questionnaire (SDM-Q-9). A general linear model was applied. Results Compared to no internet use, longer internet use was associated with a higher SDM-Q-9 score: <1 h, 6.9 points (95% confidence interval [CI] 0.32 to 13.6) and ≥2 h, 8.75 points, (95% CI 0.61 to 16.9). The SDM-Q-9 did not differ between the individuals who chose physicians and those who chose the Internet as their preferred first source of health information (–2.1 points, 95% CI –6.7 to 2.6). Individuals who chose other media had significantly lower SDM-Q-9 scores than those who chose physicians (–7.6 points, 95% CI –13.2 to –1.9). Conclusions The present study suggests that SDM between physicians and patients is positively associated with online information-seeking behavior, with no negative influence associated with accessing the Internet before clinical consultations. Rheumatologists may need to introduce their patients to websites offering high-quality health information to establish a good physician–patient relationship for SDM.