Manual therapy is effective for reducing cervicogenic dizziness, a disabling and persistent problem, in the short term. This study investigated the effects of sustained natural apophyseal glides (SNAGs) and passive joint mobilisations (PJMs) on cervicogenic dizziness compared to a placebo at 12 months post-treatment. Eighty-six participants (mean age 62 years, standard deviation (SD) 12.7) with chronic cervicogenic dizziness were randomised to receive SNAGs with self-SNAGs (n = 29), PJMs with range-of-motion (ROM) exercises (n = 29), or a placebo (n = 28) for 2-6 sessions over 6 weeks. Outcome measures were dizziness intensity, dizziness frequency (rated between 0 [none] and 5 [>once/day]), the Dizziness Handicap Inventory (DHI), pain intensity, head repositioning accuracy (HRA), cervical spine ROM, balance, and global perceived effect (GPE). At 12 months both manual therapy groups had less dizziness frequency (mean difference SNAGs vs placebo -0.7, 95% confidence interval (CI) -1.3, -0.2, p = 0.01; PJMs vs placebo -0.7, -1.2, -0.1, p = 0.02), lower DHI scores (mean difference SNAGs vs placebo -8.9, 95% CI -16.3, -1.6, p = 0.02; PJMs vs placebo -13.6, -20.8, -6.4, p < 0.001) and higher GPE compared to placebo, whereas there were no between-group differences in dizziness intensity, pain intensity or HRA. There was greater ROM in all six directions for the SNAG group and in four directions for the PJM group compared to placebo, and small improvements in balance for the SNAG group compared to placebo. There were no adverse effects. These results provide evidence that both forms of manual therapy have long-term beneficial effects in the treatment of chronic cervicogenic dizziness.