People with Locked-In Syndrome (LIS) have neuromuscular disabilities. Due to these lost and other situations, the concept of Brain-Computer Interface (BCI) established which translate brain waves activity to meaningful commands. One of the BCI applications is P300 speller that provides an alternative communication way for people with neuromuscular disabilities. The spelling process begins with presenting a screen of characters with Row-Column (RC) flashes, Single Character (SC) flashes, or Region-Based (RB) flashes, while recording and processing brain signals, and whenever a change in the signals is detected the system will recognize the desired target. P300 speller began with a single layer paradigm, then researchers developed a multi-layer paradigm which recorded higher accuracy. High accuracy increases time-consuming that results in a poor spelling process. As a result, this effort studied the effect of the user’s mother language in the spelling performance. Two healthy participants experienced in our study that was developed using BCI2000. The spelling process has been done with two spellers: Arabic and English, using RC flashes. The results of spelling with user’s mother language, and spelling with foreign language seems to be effected by the length of the word, e.g. ”Love” in Arabic will be spelt faster than ”Love” in English, as it consists of two letters in the Arabic word, whereas it is four letters in the English word. The study concluded that, the length of the word is the main factor that may affect the spelling performance.