Parkinson's disease (PD) is a neurodegenerative, with heterogeneous clinical conditions and motor changes that reduce functioning. Postural instability is one of the motor aspects of disease progression, with a potential increase in the risk of falls, consequently affecting the activities of daily living (ADL). The objective of this study was to verify the influence of a multimodal intervention program (MIP) sequentially applied in aquatic- (AEs) and land-based environments (LEs) on balance, postural control, motor activities, and ADL in people with PD. It is an interventional clinical study with patients in stages 1 to 4 in the Hoehn and Yahr scale, assessed with Berg Balance Scale (BBS), Mini-Balance Evaluation System Test (Mini-BESTest), Unified Parkinson's Disease Rating Scale (UPDRS) II and III, Dynamic Gait Index (DGI), and quiet stance (QS) analysis in a force platform. The MIP was conducted sequentially with aquatic- (AIs) and land-based interventions (LIs) for 12 weeks each, twice a week, each session lasting 1 hour, and a 12-week interval between interventions. The comparison analysis was made with Friedman ANOVA, and the multiple comparisons with Wilcoxon signed-rank, Bonferroni correction, and effect size (). The sample comprised 18 people with PD (66.83 ± 11.74 years). The AI and the full intervention (FI) had a large effect according to BBS. With Mini-BESTest, the LI and FI had a large effect. According to UPDRS II, the MIP improved ADL after LI, with a medium effect, and the motor aspects of UPDRS III improved after LI and FI, with a large effect. DGI was not sensitive in the analyses, with a ceiling effect after FI. No differences were identified in QS analyses. This research identified improved balance, ADL, and motor aspects in people with PD after sequential MIP in AI and LI, indicating that land-based and aquatic interventions are complementary and advantageous to people with PD.