This research was intended to investigate the structural feature, antioxidative activity and interaction with β-lactoglobulin (β-lg) of a polysaccharide (
P
) isolated from
Borassus flabellifer
fruit thru aqueous extraction, protein elimination and chromatographic techniques. Polysaccharide
P
(molecular weight: 21,000 g mol
−1
) was constituted of arabinose, galactose, glucose, and rhamnose in a 50:24:20:6 M ratio alongside 9% (w/w) galacturonic acid. It encompassed a petite backbone entailing galacturonopyranosyl and rhamnopyranosyl units substituted with sizable side chains comprising of arabinofuranosyl, galactopyranosyl and esterified coumaric acid (CA) residues. Various series of oligosaccharides including (i) Gal
1,2,4-9
Ac
5-29
, (ii) Ara
2-3
Ac
6-8
, (iii) Gal
3
Ara
1-3
Ac
13-17
, (iv) Gal
4-6
Ara
2
Ac
18-24
, (v) Gal
6
Ara
1
Ac
22
and (vi) Gal
1
Ara
2
CA
1
Ac
7
and Gal
1
Ara
3
CA
1
Ac
9
epitomizing polysaccharide structure were generated and characterised. Fraction
P
exhibited dose-dependent antioxidant activity and possessed a strong β-lactoglobulin binding capability. Accordingly,
B. flabellifer
fruit offers an antioxidative polysaccharide having novel structure that can associate with β-lg and, hence, useful in formulating novel food possessing adjustable composition.