There is significant phonological variation among the various Yiddish dialects. The description that follows is of a modern Standard Yiddish that was devised during the early 20th century and is frequently encountered in pedagogical contexts.

• /m, p, b/ are bilabial, whereas /f, v/ are labiodental.^[1]
• The /l – ʎ/ contrast has collapsed in some speakers.^[1]
• The palatalized coronals /nʲ, tsʲ, dzʲ, tʃʲ, dʒʲ, sʲ, zʲ/ appear only in Slavic loanwords.^[1] The phonemic status of these palatalised consonants, as well as any other affricates, is unclear.
• /k, ɡ/ and [ŋ] are velar, whereas /j, ʎ/ are palatal.^[1]
  • [ŋ] is an allophone of /n/ after /k, ɡ/, and it can only be syllabic [ŋ̍].^[1]
  • [ɣ] is an allophone of /χ/ before /b, d, ɡ, v, z, ʒ/.^[2]
• The phonetic realization of /χ/ and /nʲ/ is unclear:
  • In the case of /χ/, Kleine (2003) puts it in the "velar" column, but consistently uses a symbol denoting a voiceless uvular fricative ⟨χ⟩ to transcribe it. It is thus safe to assume that /χ/ is phonetically uvular [χ].
  • In the case of /nʲ/, Kleine (2003) puts it in the "palatalized" column. This can mean that it is either palatalized alveolar [nʲ] or alveolo-palatal [ɲ̟]. /ʎ/ may actually also be alveolo-palatal [ʎ̟], rather than just palatal.
• The rhotic /r/ can be either alveolar or uvular, either a trill [r ~ ʀ] or, more commonly, a flap/tap [ɾ ~ ʀ̆].^[1]
• The glottal stop [ʔ] appears only as an intervocalic separator.^[1]

As in the Slavic languages with which Yiddish was long in contact (Russian, Belarusian, Polish, and Ukrainian), but unlike German, voiceless stops have little to no aspiration; unlike many such languages, voiced stops are not devoiced in final position.^[1] Moreover, Yiddish has regressive voicing assimilation, so that, for example, זאָגט /zɔɡt/ ('says') is pronounced [zɔkt] and הקדמה /hakˈdɔmɜ/ ('foreword') is pronounced [haɡˈdɔmɜ].

The vowel phonemes of Standard Yiddish are:

• /ɪ, ʊ/ are typically near-close [ɪ, ʊ] respectively, but the height of /ɪ/ may vary freely between a higher and lower allophone.^[3]
• /ɜ/ appears only in unstressed syllables.^[3]

• The last two diphthongs may be realized as [aɛ] and [ɔɜ], respectively.^[3]

In addition, the sonorants /l/ and /n/ can function as syllable nuclei:

• אײזל /ˈɛɪzl̩/ 'donkey'
• אָװנט /ˈɔvn̩t/ 'evening'

[m] and [ŋ] appear as syllable nuclei as well, but only as allophones of /n/, after bilabial consonants and dorsal consonants, respectively.

The syllabic sonorants are always unstressed.

In vocabulary of Germanic origin, the differences between Standard German and Yiddish pronunciation are mainly in the vowels and diphthongs. All varieties of Yiddish lack the German front rounded vowels /œ, øː/ and /ʏ, yː/, having merged them with /ɛ, e:/ and /ɪ, i:/, respectively.

Diphthongs have also undergone divergent developments in German and Yiddish. Where Standard German has merged the Middle High German diphthong ei and long vowel î to /aɪ/, Yiddish has maintained the distinction between them; and likewise, the Standard German /ɔʏ/ corresponds to both the MHG diphthong öu and the long vowel iu, which in Yiddish have merged with their unrounded counterparts ei and î, respectively. Lastly, the Standard German /aʊ/ corresponds to both the MHG diphthong ou and the long vowel û, but in Yiddish, they have not merged. Although Standard Yiddish does not distinguish between those two diphthongs and renders both as /ɔɪ/, the distinction becomes apparent when the two diphthongs undergo Germanic umlaut, such as in forming plurals:

The vowel length distinctions of German do not exist in the Northeastern (Lithuanian) varieties of Yiddish, which form the phonetic basis for Standard Yiddish. In those varieties, the vowel qualities in most long/short vowel pairs diverged and so the phonemic distinction has remained.

Yiddish has some coincidental resemblances to Dutch in vowel phonology, which extend even to orthography, such as Dutch ij versus Yiddish tsvey judn, both pronounced /ɛɪ/; and Dutch ui (pronounced /œy/) versus Yiddish vov yud (/ɔj/). For example, the Yiddish "to be" is זיין, which orthographically matches Dutch zijn more than German sein, or Yiddish הויז, "house", versus Dutch huis (plural huizen). Along with the pronunciation of Dutch g as /ɣ/, Yiddish is said to sound closer to Dutch than to German because of that even though its structure is closer to High German.^{[citation needed]}

There are consonantal differences between German and Yiddish. Yiddish deaffricates the Middle High German voiceless labiodental affricate /pf/ to /f/ initially (as in פֿונט funt, but this pronunciation is also quasi-standard throughout northern and central Germany); /pf/ surfaces as an unshifted /p/ medially or finally (as in עפּל /ɛpl/ and קאָפּ /kɔp/). Additionally, final voiced stops appear in Standard Yiddish but not Northern Standard German.

The pronunciation of vowels in Yiddish words of Hebrew origin is similar to Ashkenazi Hebrew but not identical. The most prominent difference is kamatz gadol in closed syllables being pronounced same as patah in Yiddish but the same as any other kamatz in Ashkenazi Hebrew. Also, Hebrew features no reduction of unstressed vowels and so the given name Jochebed יוֹכֶבֶֿד would be /jɔɪˈχɛvɛd/ in Ashkenazi Hebrew but /ˈjɔχvɜd/ in Standard Yiddish.

Patah in open syllable, as well as hataf patah, are unpredictably split between A₁ and A₂: קַדַּחַת, נַחַת /kaˈdɔχɜs, ˈnaχɜs/; חֲלוֹם, חֲתֻנָּה /ˈχɔlɜm, ˈχasɜnɜ/.