In forensic toxicology, drugs of abuse are routinely analyzed due to legal statute in medical or legal investigation, such as death cases, poisoning cases, and drug misuse, determining potential exposure to controlled substances. Despite the widespread use of blood and urine as matrices for forensic toxicological analysis, the use of hair samples has grown as the limitations associated with this matrix are overcome and new areas of application emerge. Hair provides several advantages over urine and blood, such as the easiness of sample collection and the ability to provide a retrospective analysis of drug consumption. Drug analysis in hair is following a path where less amount of sample has been needed to detect drugs of abuse. Improvement in sample preparation methods and lowering detection limits in instrumental analysis is providing forensic scientists with the tools to use drug analysis with hair as a routine approach in the forensic laboratory. Actually, besides the chronological exposition to a drug, hair may provide information about the day a chemical was used. This should become part of the standard information sent by forensic scientists to criminal investigators and courts. The aim of this review is to summon the extraction procedures used to perform forensic toxicological analysis in hair as well as the major advances in this field once a sample preparation step is critical and takes up most of the total analysis time.