B cells play a critical role in the immune response by producing antibodies, which display remarkable diversity. Here we describe a bioinformatic pipeline, BALDR (BCR Assignment of Lineage using De novo Reconstruction) that accurately reconstructs the paired heavy and light chain immunoglobulin gene sequences from Illumina single-cell RNA-seq data. BALDR was accurate for clonotype identification in human and rhesus macaque influenza vaccine and simian immunodeficiency virus vaccine induced vaccine-induced plasmablasts and naïve and antigen-specific memory B cells. BALDR enables matching of clonotype identity with single-cell transcriptional information in B cell lineages and will have broad application in the fields of vaccines, human immunodeficiency virus broadly neutralizing antibody development, and cancer.BALDR is available at https://github.com/BosingerLab/BALDR .