Chinese vs Cantonese
Learn Chinese and Cantonese at the same time
Mandarin and Cantonese are both Chinese (Sinitic) languages that share most of their characters and a formal written standard, but in speech they are not mutually intelligible: Cantonese has six tones, different everyday vocabulary and grammar particles.
The short answer
Yes, many people do, usually Mandarin first. Shared characters and vocabulary help, but similar words with different tones and readings cause real interference. Use Pinyin for Mandarin and Jyutping for Cantonese, and separate the languages by time or context.
The verdict
A strong combination: Mandarin first, then Cantonese reuses characters and grammar. Expect tone interference for a while.
Closeness score
20 / 30
Mutually intelligible?
partly
Shared vocabulary
Formal vocabulary is largely shared; everyday spoken vocabulary diverges considerably
Which first?
Mandarin first unless you live in Hong Kong / Guangdong.
Kungfucius says: Same family dinner, different dinner-table language.
Side by side
chī食
sik6食 is the older word (Classical Chinese); Mandarin replaced it with 吃 in everyday speech but keeps 食 in compounds such as 食物.
bù / de唔 / 嘅
m4 / ge3These characters exist almost only in written Cantonese, so their presence identifies the text immediately.
shì係
hai6Cantonese uses 係 as its everyday copula; Mandarin uses 是.