Currently, there are no objective measures available to support the clinical diagnosis of bipolar disorder (BD), as this condition is diagnosed based purely on clinically based behavioral and psychological assessments. Therefore, the investigation of biomarkers in BD has gained increasing attention and significance due to its potential to help aid in diagnosis, distinguish between mood phases in BD, and guide pharmacological management. The technological advances made in the field have significantly influenced and propelled biomarker research in BD. This chapter delves into the main classes of blood biomarkers under investigation in BD, explores how the field of “omics” research is propelling significant advancements, and examines the potential utilization and limitations of implementing biomarkers in clinical practice.