The objective of this paper is to examine the extent to which verbal extensions in Limbum affect valency. Limbum is a Grassfield Bantu language of the Northern group, spoken by the population who occupy a greater part of the Nkambe plateau in Donga-Mantung Division of the North West Region of Cameroon Binan Bikoi (ed) (2012). To attain my set objective, I carry out an analysis of those affixes (in the case of Limbum, they are suffixes), which are usually attached to verbs and the effect the addition of these suffixes has on the number of arguments in the sentence. Some of these suffixes have a valency decreasing effect, while some have a valency increasing effect on the verbs. The orientation of the discussions here centres on the description of the morpho-syntactic structure of the Limbum verb. In this regard, the analysis herein draws inspiration from the theory of Valency as proposed by Tesnière in 1959 and his followers and the Structuralist Framework as propounded by De Saussure and his disciples who hold that linguistic unit: words, phrases and sentences are perceived as a concatenation of smaller units which hold a close relationship between them. The structure of the Limbum sentence containing verbal extensions that express aspectual meanings have three consequences on the number of arguments that the verb takes: the discussions here show that, while the morphemes -ri, -Si, and -se marking the attenuative, the pluractional, and the distributive aspects respectively have no effect on the number of arguments taken by the verb to which they are suffixed, the causative morpheme -si, has a valency increasing effect on the verb to which it is affixed. In the same light, the reciprocative -ni, the separative -ti and the iterative -Nger, when suffixed to a verb, have the tendency of increasing the number of arguments that the verb takes. In a bid to clarify the structural cartography of verbal extensions in Limbum, the last part of this paper is dedicated to a presentation of some suffixes like -ri and -si, which has, with the evolution of the language, fossilized with the verb root to the extent that they have become an integral part of the verb in a way that they cannot be detached from each other. Conclusively, the paper shows that verbal extensions in Limbum are, for the most part, suffixal morphemes. While some of these suffixes have no effect on the number of arguments the verb subcategorizes for, some have a valency decreasing effect on the verb while others, on the other hand, have a valency increasing effect. Others have outrightly merged with the verb root.