Adjectives agree with the nouns they modify in gender, case, and number. But the adjective at times agrees with the natural gender of the referent, rather than with the gender of the noun representing it. Consider the following example, where the feminine noun handugei 'wisdom' is modified by a neuter adjective agreeing with the genderless concept represented by handugei: ei kanniþ wesi handugei guþs 'that the wisdom of God be known'. Note also the following, where neuter áinhun (leike) 'any (of bodies)' is modified by a masculine singular adjective taking its gender from the person or man whom the circumlocution represents: ni wairþiþ garaihts áinhun leike 'no man becomes just'.

When a singular noun denotes a collection of individual members, the adjective may take its number and gender according to the individuals. For example, the feminine singular managei 'multitude, people' is generally modified by adjectives in the masculine plural: jah was managei beidandans Zakariins 'and the people were waiting for Zacharias'. This likewise occurs with the noun hiuhma 'crowd': jah alls hiuhma was manageins beidandans 'and the whole crowd of people was waiting'.

Unlike many of the Indo-European languages, but like e.g. Old Norse, an adjective modifying both masculine and feminine beings takes a neuter plural form. For example, wesunuh þan garaihta ba andwairþja guþs 'they were both righteous before God', where the referents are Zacharias and Elizabeth.

Adjectives take either strong or weak endings. Strong adjective forms modify indefinite nouns. Consider the following examples: stibnái mikilái 'in a loud voice'; gaguds ragineis 'a good counselor'; wastjái ƕeitái 'in a white cloth'. Predicate adjectives regularly take strong endings: goþ þus ist hamfamma in libáin galeiþan 'it is better for thee to enter into life maimed'. All cardinal numerals only decline strong, as well as the ordinal anþar 'second'; likewise the possessive adjectives like meins 'my'; pronominal adjectives like sums 'some', alls 'all', jáins 'that', swaleiks 'such'; and other adjectives like fulls 'full', ganóhs 'enough', halbs 'half', midjis 'middle'.

Weak adjective forms modify definite nouns, and therefore generally accompany the definite article. For example, stiur þana alidan 'the fattened calf'; (áina) anabusne þizo minnistóno '(one) of the smallest commandments'; wastja þó frumistōn 'the best garment'; ni mag bagms þiuþeigs akrana ubila gatáujan 'a good tree cannot bear evil fruits'. A weak adjective generally accompanies a noun in the vocative: atta weiha 'holy father!'; o unfrodans Galateis 'O foolish Galatians'. All ordinal numerals beside anþar exhibit only weak declension. The same is true for comparatives, as well as intensives ending in -ma, e.g. aftuma 'latter'. The present participle takes weak endings, except for the alternate strong ending in the masculine nominative singular. The adjectives sama 'same' and silba 'self' always take weak endings.