Short answer. No. The law looks at the actual work you perform, not the label in your contract. An employee engaged in activities usually necessary or desirable to the employer's usual business is deemed regular, regardless of what a written or oral agreement calls that arrangement.
What the law says
The provisions of written agreement to the contrary notwithstanding and regardless of the oral agreement of the parties, an employment shall be deemed to be regular where the employee has been engaged to perform activities which are usually necessary or desirable in the usual business or trade of the employer
Labor Code, Article 280 — Regular And Casual Employment. Read the full provision →
The contract's label does not override the actual work
This article is written specifically to stop a job title or contract label from deciding the question. It says regular status applies "the provisions of written agreement to the contrary notwithstanding and regardless of the oral agreement of the parties," as long as you were engaged to perform activities "usually necessary or desirable in the usual business or trade of the employer." If what you actually do fits that description, calling you "casual" in the paperwork does not change your legal status.
Two narrow exceptions where the label can matter
The article does recognize two situations where employment is not automatically regular even if the work fits that general description: where the employment "has been fixed for a specific project or undertaking the completion or termination of which has been determined at the time of the engagement," and where the work is "seasonal in nature and the employment is for the duration of the season." These are specific, defined exceptions — not a general escape hatch for any employer who prefers to call staff "casual."
What "casual" actually means under this article
The article defines casual employment narrowly, as a leftover category: "an employment shall be deemed to be casual if it is not covered by the preceding paragraph." In other words, casual status is not something an employer can declare outright — it only applies to employment that genuinely falls outside the regular-employment description and outside the project or seasonal exceptions. If your actual duties are necessary or desirable to the employer's usual business, the casual label does not fit you to begin with.
One year of service converts the status regardless
Even setting the label question aside, the article adds a separate safety net: "any employee who has rendered at least one year of service, whether such service is continuous or broken, shall be considered a regular employee with respect to the activity in which he is employed and his employment shall continue while such activity exists." So even if your work genuinely started out as casual, reaching a year of service on that same activity converts your status to regular by operation of this article, independent of anything the contract says.