The global population of multimorbid older people is growing steadily. Multimorbidity is the principal cause of complex polypharmacy, which in turn is the prime risk factor for inappropriate prescribing and adverse drug reactions and events. Those who prescribe for older frailer multimorbid people are particularly prone to committing prescribing errors of various kinds. The causes of prescribing errors in this patient population are multifaceted and complex, including prescribers' lack of knowledge of aging physiology, geriatric medicine, and geriatric pharmacotherapy, overprescribing that frequently leads to major polypharmacy, inappropriate prescribing, and inappropriate drug omission. This review examines the various ways of minimizing prescribing errors in multimorbid older people. The role of education in physician prescribers and clinical pharmacists, the use of implicit and explicit prescribing criteria designed to improve medication appropriateness in older people, and the application of information and communication-technology systems to minimize errors are discussed in detail. Although evidence to support any single intervention to prevent prescribing errors in multimorbid elderly people is inconclusive or lacking, published data support focused prescriber education in geriatric pharmacotherapy, routine application of STOPP/START (screening tool of older people's prescriptions/screening tool to alert to right treatment) criteria for potentially inappropriate prescribing, electronic prescribing, and close liaison between clinical pharmacists and physicians in relation to structured medication review and reconciliation. Carrying out a structured medication review aimed at optimizing pharmacotherapy in this vulnerable patient population presents a major challenge. Another challenge is to design, build, validate, and test by clinical trials suitably versatile and efficient software engines that can reliably and swiftly perform complex medication reviews in older multimorbid people. The European Union-funded SENATOR and OPERAM clinical trials commencing in 2016 will examine the impact of customized software engines in reducing medication-related morbidity, avoidable excess cost, and rehospitalization in older multimorbid people.