The present research study mainly aims to investigate the first language interference in Arabic-English translation and the potential factors behind such translational practice. The researcher gives a special attention to lexical and syntactical translational mistakes and errors. This includes, on one hand, the lexical errors and mistakes occurred in the collocations, word-choice, and tautology. On the other hand, it investigates syntactical errors and mistakes in terms of punctuations and transitional connectors. To this affect, the researcher utilized two sources of data for reliable and valid outcomes. Therefore, in one hand, he used randomly selected texts made available before being edited, revised, and published at the official website of Islamic Military Counter Terrorism Coalition www.imctc.org albeit claimed finalized and problem-free by seven translators, consisting of more than 12000 words. All selected translated texts were holistically processed to figure out the translational mistakes and the potential reasons for that in order to reflect on the outlined research questions. On the other hand, a self-constructed survey was designed for the purpose of the research. The seven translators of the intended website were individually interviewed in face-to-face discussion. The results revealed that the FL interferences heavily impacted on the lexical errors and mistakes (collocations, word-choice, and tautology) and the syntactical errors and mistakes (punctuations and transitional connectors) for different reasons and factors contributory to producing poor translation. The researcher suggested some points to be considered by existing and potential translation practitioners and academics.