Background Many patients with hematological malignancies treated with stem cell transplantation (SCT) experience cognitive dysfunction. However, few studies have investigated treatment-related neurotoxicity in older adults with multiple myeloma (MM) treated with high dose chemotherapy (HDC) and autologous SCT (HDC/ASCT). In this study, we examined gray matter (GM) volume, resting state functional connectivity (RSFC), neurocognitive function (NF), and proinflammatory cytokines (PCy) in older patients with MM pre- and post-HDC/ASCT. Methods Eighteen MM patients underwent magnetic resonance imaging, neurocognitive tests, and serum PCy measurement prior to HDC/ASCT, and fifteen patients completed follow ups an average of five months post-HDC/ASCT. Results There were significant decreases in RSFC from pre- to post-HDC/ASCT in (1) the central executive network (CEN) involving the dorsolateral prefrontal cortex and posterior parietal cortex (p = 0.022), and (2) the CEN involving the posterior parietal cortex and the salience network involving the dorsal anterior cingulate cortex (p = 0.029); these comparisons were no longer significant after multiple comparisons correction. There were no significant changes in GM volumes or NF, except for improvement in attention (Digit Span Backward, p = 0.03). There were significant increases in several PCy post-HDC/ASCT (p ≤ 0.05). Conclusions This pilot study showed decreased RSFC involving the left frontal, right posterior parietal and right anterior cingulate cortices in MM patients post-HDC/ASCT, relatively stable NF, and increases in PCy. These findings are congruent with studies in patients with hematological malignancies and other cancers and provide supporting evidence for the vulnerability of frontoparietal regions to chemotherapy adverse effects.