The processing of green coffee for the extraction of polyphenols resulted in green coffee spent (GCS) accounting 90% dietary polysaccharides. The GCS rich in Non-digestible carbohydrates (oligosaccharides) represent promising prebiotic nutrients. These Non-digestible oligosaccharides were extracted and characterized for valorization of the GCS. The enzymatic (Viscozyme), thermal (roasting) and aqueous (hot water infusion) extraction yielded 19.92?±?2.1% of Mono-oligosaccharides with mannose (6.90?±?0.9?μg/Mg) and galactose (8.35?±?1.0?μg/Mg) as major components. Further, the GCS oligosaccharides were evaluated for prebiotic efficiency using Lactobacillus species (L. plantarum, L. casei and L. fermentum). The GCS oligosaccharides also stimulated the growth of Lactobacillus casei (MTCC 1423) and Lactobacillus fermentum (MTCC 903) by increasing their number from 8.96 Log CFU/ml to 9.82 Log CFU/ml and from 8.97 Log CFU/ml to 9.66 Log CFU/ml respectively. The maximum utilisation of Mannose (70%) and galactose (66%) was observed in L. plantarum. Additionally GCS oligosaccharides tested for acid resistance and found resistant towards artificial human gastric juice. The non-digestibility of GCS oligosaccharides noted 90% at pH 1. This study provides insights about bio-sustainable approach of use of GCS in designing synbiotic functional food.