This work looks into the language acquisition of a four (4) years old girl child in a bilingual situation to ascertain the level of her bilingual (i.e Nigerian English and Igbo languages acquisition as she lives within Nsukka urban area where these two languages are spoken) in respect to phonology, semantics, morphology and syntax of both languages. According to Agbedo (2009), language acquisition of bilinguals can be said to be a controversial phenomenon, this is because while some scholars support it, others condemn it saying that in most cases, the dominant language affects the acquisition of the other language. This study adopted the unstructured interview method in the data collection while the descriptive approach was used in the analysis of the data collected. However in the theoretical framework, it was ascertained that though most of the these theorists/scholars did not have the bilinguals in mind while propounding their theories, yet these theories also affect the bilinguals and even the multilinguals as all normal children all over the world display similar linguistic achievements at about thesame age in life regardless of he/she being a Mono, bi or multilingual. The findings of the study reveals that the child understudied was exposed early enough to both languages by her parents who are literates and are living in a rich linguistic environment and this made her to be fast in acquiring both languages simultaneously. Her choice of words in answer to questions posed to her indicates a high rate of acquisition that is above average. After analysing the language acquisition issues relating to the investigated child, it was found out that she is now in her semantic acquisition level as she has started attaching meaning to what she hears or produces and she also understands questions statements, requests, commands and other communication situations in both languages and these are the most important and difficult aspect in language development. In conclusion, after appraising this four year old girl child under investigation, as a bilingual, her abilities and disabilities as regards to her phonological, morphological, syntactic and semantic developments of both languages were observed, pointed out and found that her rate of development is high at four years and based on the findings we therefore, recommend that this child and her likes who will present such high rate of intelligent quotient and linguistic development present the need to be fanned for later general academic excellence and therefore require immediate attention and follow-up both at home and in the school by her parents, care givers and teachers. Governments should also sponsor scholars from different ethnic groups, tribes and languages to embark on such study as this, as it will help to reduce some communication gaps between people of different languages but of same nation. Parents, caregivers, teachers and even neighbours are also encouraged to speak both a child’s mother tongue and the official language of a nation to a child as this will help him or her cope very well in communication within and outside his/her immediate environment.