This study has looked at intraparty politics in Kenya through different transitional periods of democracy since 1921. It is premised on the fact that. in as. much as intra-party democracy is a desirable ideal for effective political party performance and consolidation of democracy in the wider society, in the context of Kenya, most of the parties have not functioned as effective institutions of democracy. This is attributed to the fact that even though principles of intra-party democracy are stipulated in the organizational rules of most parties, they have not been practically implemented in the actual political processes. Thus even the celebrated re-introduction of multi-party democracy in Kenya since 1991 has simply produced a discontinuity in the life of democratic transition with increasingly unpopular and distrusted parties. Very few studies have examined the status of internal democracy in political parties over the different transitional periods. Furthermore, the effects of intra-party democracy in transition to democracy have not been adequately analysed in light of the performance of individual political parties and yet parties tend to be amongst the least trusted institutions in Kenya, often plagued by internal conflicts and suspected to be guided more by the pursuit of power than ideology or principle. This study therefore sought to investigate developments of intra-party democracy in Kenya since 1921. analyze the developments and challenges of intra-party democracy in Kenya since 1991, discuss the meaning and practice of intra-party democracy in the context of Kenyan political parties since 1921. assess the contributions and challenges of political parties towards the realization of sustainable intra-party democracy in Kenya, examine the content of the constitutions and manifestos of political parties in Kenya and assess opinions on the status of their institutional arrangements. Descriptive design was used in the study. Purposive Sampling was used to select four parties (KANU. TNA, ODM and FORD-Kenya) on the basis of membership representation in parliament, and degree of organization and participation in National presidential elections. Primary data was collected using questionnaires (300), Focus Group Discussions (9), key informant interviews (119) and expert opinion interviews (10) from members of different political parties in constituencies randomly selected from four counties in Kenya (Kisumu, Bungoma, Nandi. and Kiambu). {:\rchiv,ll information was also used as part of primary data. Secondary data was collected from party documents. general review of media reports and commentaries on party activities. Being a mixed methods research, thematic and content analysis was used for qualitative data to develop comprehensive description of phenomena under study. Transcribing, corroboration and validation of results was done from both secondary and primary data throughout the data collection, analysis and write up. Organization theory and institutional theory which analyzes internal organizational structures and institutions of political parties were considerd relevant in this study. The study shows that successive political regimes have often downplayed their significance through political patronage and politics built on ethnic alliances and rivalries among political elites over approach to power. While parties have influenced transition to democracy in Kenya, their poor status of internal democracy has often downplayed their significance in consolidation of democracy. It also observes that the performance of political parties continue to manifest a huge gap between their constitutional prescriptions and actual implementation thus calling for constitutional regulation of their conduct. The study concludes that political parties should be recognized as institutions of democracy and central determinants in transition to democracy in order 10 reconcile the myriad of conflicting demands of individuals, groups, interests, communities and regions in Kenya.