This paper identifies the acquisition order of seven grammatical morphemes of Amharic and analyses thernmost recurrent grammatical errors (phonological and morpho-syntactic errors) committed by the targetrngroup. The subjects of this study were 45 adult monolingual American English-speaking learners ofrnAmharic as a second language at Joint Language School. They were selected via purposive samplingrntechnique from four phases. This research employed Cross-sectional Research Design. The elicitationrntechniques were: (i) Structural Natural Conversation (guided by Bilingual Syntax Measure) to gather datarnfor morpheme acquisition order analysis. In this case, both oral and written testes were given for therntarget group; (ii) Unstructured Natural Conversation (through picture description, storytelling andrnclassroom speech) was used to collect the data which was utilized to analyze the regular and logical errorsrncommitted by the subjects. Following this, on one hand, the acquisition order of seven grammaticalrnmorphemes was analyzed using Group Score Method which is developed by Dulay and Burt (1974). Thisrnpart of the analysis was also accompanied by two scoring systems: (i) Scoring System One: which gives 2rnpoints for correct morpheme, 1 point for malformed morpheme and 0 point for no morpheme; (ii) ScoringrnSystem two: which awards 2 points for correct morpheme and correct vocabulary but assigns 0 point forrnother cases. On the other hand, the errors were analyzed based on Creative Construction and ContrastivernAnalysis theories. The study revealed that: (i) There is an acquisition order of grammatical morphemes.rnFor instance, the plural marker /-oÄÄ/ and the passive marker /t -/ are acquired earliest and latest amongrnthe investigated seven grammatical morphemes respectively. (ii) The learners’ grammatical competencernin Amharic phonology, morpho-syntax is low, and (iii) the errors were caused by such factors as therninconsistency in the morphological rules of Amharic, overgeneralization of the target langue rules,rnmisapplication of rules as well as the interference of the subjects’ mother tongue to Amharic. This findingrnwill have significant contribution: (i) to widen and develop the roles of Amharic for Ethiopianrnsocioeconomic development; and (ii) for pedagogical purposes such as: textbook preparation, curriculumrndesigning, teaching method development, and test items preparation. The study offered certain feasiblernrecommendations based on the conclusion and indicated further research areas too