The genetic basis of Alzheimer's disease (AD) is complex and heterogeneous. Over 200 highly penetrant pathogenic variants in the genes APP, PSEN1, and PSEN2 cause a subset of early-onset familial AD. On the other hand, susceptibility to late-onset forms of AD (LOAD) is indisputably associated to the ɛ4 allele in the gene APOE, and more recently to variants in more than two-dozen additional genes identified in the large-scale genome-wide association studies (GWAS) and meta-analyses reports. Taken together however, although the heritability in AD is estimated to be as high as 80%, a large proportion of the underlying genetic factors still remain to be elucidated. In this study, we performed a systematic family-based genome-wide association and meta-analysis on close to 15 million imputed variants from three large collections of AD families (~3500 subjects from 1070 families). Using a multivariate phenotype combining affection status and onset age, meta-analysis of the association results revealed three single nucleotide polymorphisms (SNPs) that achieved genome-wide significance for association with AD risk: rs7609954 in the gene PTPRG (P-value=3.98 × 10-8), rs1347297 in the gene OSBPL6 (P-value=4.53 × 10-8), and rs1513625 near PDCL3 (P-value=4.28 × 10-8). In addition, rs72953347 in OSBPL6 (P-value=6.36 × 10-7) and two SNPs in the gene CDKAL1 showed marginally significant association with LOAD (rs10456232, P-value=4.76 × 10-7; rs62400067, P-value=3.54 × 10-7). In summary, family-based GWAS meta-analysis of imputed SNPs revealed novel genomic variants in (or near) PTPRG, OSBPL6, and PDCL3 that influence risk for AD with genome-wide significance.