Short answer. Generally yes. A party may assert in one pleading as many causes of action as he has against an opposing party. But the joinder has conditions: it must respect the rules on joinder of parties, it cannot include special civil actions or actions governed by special rules, and jurisdiction and venue requirements must still be satisfied.
What the law says
A party may in one pleading assert, in the alternative or otherwise, as many causes of action as he may have against an opposing party
Rule 2, Section 5 — Joinder of causes of action. Read the full provision →
What the law says
Where the claims in all the causes of action are principally for recovery of money, the aggregate amount claimed shall be the test of jurisdiction.
Rule 2, Section 5 — Joinder of causes of action. Read the full provision →
Joinder is allowed, and even in the alternative
The Rules let a party in one pleading assert, in the alternative or otherwise, as many causes of action as he may have against an opposing party. So a creditor owed on three separate loans, or a lessor with claims for unpaid rent and for damage to the premises, can put everything in one complaint instead of financing several suits. The phrase in the alternative matters too: you may plead inconsistent theories — for example, recovery on a contract or, failing that, on some other basis — and let the evidence determine which one succeeds.
The claims that cannot ride along
Joinder is a privilege with boundaries. The joinder shall not include special civil actions or actions governed by special rules — those cases follow their own tailored procedures and cannot be folded into an ordinary suit. The party joining causes of action must also comply with the rules on joinder of parties, which becomes relevant the moment the claims involve different combinations of plaintiffs or defendants rather than a clean one-on-one dispute. If one of your claims belongs to a special track, expect to file it separately no matter how convenient a single complaint would be.
Jurisdiction and venue still control
Where the causes of action pertain to different venues or jurisdictions, the rule allows the joinder in the Regional Trial Court provided one of the causes of action falls within the jurisdiction of said court and the venue lies therein. And for money claims there is a distinctive arithmetic: where the claims are principally for recovery of money, the aggregate amount claimed shall be the test of jurisdiction. Several modest claims can therefore add up to the Regional Trial Court's threshold even though each, filed alone, would have gone to a first-level court. Which court you can file in may change depending on whether you join or split.
Deciding whether to join everything
Joinder usually saves filing fees, time, and the risk of inconsistent findings, so combining claims against the same person is the sensible default. But run each claim through the conditions first: is any of them a special civil action, do the parties line up, and where does the aggregate amount place jurisdiction? A complaint that joins what cannot be joined invites a procedural fight before the merits are ever reached. A lawyer will want to see the documents behind each claim — contracts, receipts, demand letters — to map which claims belong together and in which court.