Physical inactivity is prevalent in older adults with type 2 diabetes mellitus (T2DM) and may exacerbate their clinical symptoms. The aim of this study was to examine the feasibility of 4-h regular versus more dynamic standing sessions while performing routine desktop activities as a non-exercise physical activity intervention in older adults with T2DM to increase non-exercise activity. Twelve older adult patients with T2DM (3 female; age 71 ± 4 years; Body mass index 34 ± 5 kg/m ) completed three sessions (baseline sitting followed by "static" or "dynamic" desktop standing sessions). Participants stood behind a regular height-adjustable desk in the "static" standing session. An upright dynamic standing desk, which provides cues to make small weight-shifting movements, was used for the "dynamic" standing session. Oxygen consumption, cognitive performance, as well as net standing duration, total movement activity, and musculoskeletal discomfort were assessed during all three sessions. All participants were able to complete all sessions. Oxygen consumption and overall movements progressively increased from sitting to static and dynamic standing, respectively (p < 0.001). The duration of breaks during standing (p = 0.024) and rate of total musculoskeletal discomfort development (p = 0.043) were lower in the dynamic standing compared to static standing sessions. There was no evidence of executive cognitive worsening during either standing session compared to sitting. Prolonged 4-h standing as a simple non-exercise physical intervention is feasible in older adults with T2DM and may have metabolic (oxygen consumption) benefits. Increasing movement during desktop standing may offer incremental benefits compared to regular standing. Prolonged desktop standing might provide an effective intervention in T2DM older participants to target sedentariness. ClinicalTrials.gov (NCT04410055), retrospectively registered May 27, 2020.