DNA-assisted proteomics technologies enable ultra-sensitive measurements in multiplex format using DNA-barcoded affinity reagents. Although numerous antibodies are available, nowadays targeting nearly the complete human proteome, the majority is not accessible at the quantity, concentration or purity recommended for most bio-conjugation protocols. Here, we introduce a magnetic bead-assisted DNA-barcoding approach, applicable for several antibodies in parallel, as well as reducing required reagents quantities up to a thousand-fold. The success of DNA-barcoding and retained functionality of antibodies were demonstrated in sandwich immunoassays and standard quantitative Immuno-PCR assays. Specific DNA-barcoding of antibodies for multiplex applications was presented on suspension bead arrays with read-out on a massively parallel sequencing platform in a procedure denoted Immuno-Sequencing (I-Seq). Conclusively, human plasma samples were analyzed to indicate the functionality of barcoded antibodies in intended proteomics applications.This article is protected by copyright. All rights reserved