Anxiety is highly prevalent among patients with rheumatoid arthritis (RA). Although this co-occurrence is associated with a range of adverse functional, mental, and physical health outcomes (e.g., more joint abnormalities, greater disease activity, higher functional disability, more severe pain and fatigue), the management of RA remains reliant on a biomedical approach. Guided by a biopsychosocial framework, this dissertation aimed to both clarify and add to the extant literature on comorbid anxiety in RA. Specifically, (1) I examined the possibility of distinct anxiety trajectory groups within an RA sample as well as unique correlates associated with group membership; and (2) I tested the feasibility and potential benefit of an accessible anxiety intervention among RA patients. Using a clinical sample of individuals with RA (N=154), Study 1 identified three distinct anxiety trajectory groups uniquely associated with a number of clinical indicators cross-sectionally and longitudinally. More severe anxiety was associated with worse outcomes (i.e., functional disability, tender joint count, pain, and fatigue) and persistent moderate anxiety was associated with worsened fatigue over time. Study 2 supported the feasibility of an Internet-based cognitive-behavioral therapy (iCBT) intervention for anxiety (and depression) in RA patients (N=34) through recruitment, adherence, and qualitative patient feedback. Preliminary evidence of mental (i.e., anxiety, depression, and emotional distress) and physical (i.e., fatigue) improvements following participation in the intervention was also provided. Results of this dissertation hold important implications for the assessment and treatment of anxiety in the context of RA. Findings are discussed in relation to a stepped care model and possible amendments to current Canadian healthcare practices are reviewed.